Ooh you sound just like me! I was introduced to SLT by our careers advisory woman, but she told me I'd need to take Biology, which I couldn't stand the thought of. I ended up taking English Lit, History and German and I got into 4/6 universities I applied for (the 2 I didn't get into, UCL and Sheffield, both called the course "speech sciences", so I wasn't overly surprised, although I did get an interview for both). In my year there was a real mix of different academic backgrounds. My best friend had taken Biology at A level and during our medicine modules she certainly said it was an advantage. I did find this aspect difficult, perhaps more difficult than some of the others, but it was by no means impossible. I think Reading is historically quite a linguistics based university (which was one of the reasons it appealed to me so much), but obviously there are certain "sciency" areas you do have to cover. In terms of this affecting how well you do and how much you enjoy the course, I ended up managing to get a first and I absolute adore speech therapy. So I definitely wouldn't write it off!
As for work experience, it's really difficult to get to shadow an actual speech therapist, because they are so difficult. So I always think it's best to try and find a way to volunteer with relevant client groups. As far as children are concerned, working with different age groups can really help- I had done work experience at a nursery and a special needs school during my year 10 work experience, and then throughout sixth form I volunteered at Brownies. With adults, your best bet is to look through charities. Before I got my job, I was volunteering with the Stroke Association at their communication rehab groups, which I loved. I just rang up my local branch and they were more than happy to help. If you google local organisations you should get a good idea of where to start.
I'm glad you liked it. As I've written here before, I absolutely loved it, can't praise it highly enough.
I know, I remember being massively daunted by the number of applicants to the number of places. It is a very competitive course, but if you have the grades, a strong personal statement, relevant experience and a real passion for the course, then I think you stand a really good chance. As you've said, obviously academically you have to make your grades and I imagine that is fairly non-negotiable. Personal statements are what they're going to use to decide whether or not you'll be short-listed. In the case of Reading, if you're short-listed you'll get a questionnaire to complete (at least you did when I applied in 2007 and I don't think that's changed). I know on here they can take a look at your PS, and I made sure I made the most of any such opportunities available at my school. I think work experience is probably something which helps differentiate between applicants- read above my suggestions for perhaps how to go about that. I would just make sure that whatever experience you do manage to get, you really explain how this will help you on the course- don't make them infer it, explain it. As well as being a competitive course, it's also a demanding course, so I think you really need to show just how keen you are to do it. Work experience shows this, but also reading relevant books (I always recommend David Crystal's Introduction to Speech and Language Pathology as a really good starting point) can definitely help.
I would definitely suggest taking your time over the questionnaire. I remember drafting my answers about a million times before filling in the actual form. Obviously always get someone to check them for any obvious spelling/grammar errors, but try to include as much as possible. I have very small writing and I remember having to really cram in my writing into those boxes, but this is your chance to sell yourself. I can't remember exactly what they asked, but make sure you're prepared to justify why it is you want to go to Reading specifically. You're one step ahead here because you went to the open day (I didn't go before applying) so hopefully you'll have lots to say here. (Sorry if it's not a questionnaire any more, but I'm sure unless you're a mature student, it is).
Good luck
It is a really competitive course, but don't let that put you off. If it's what you want to do, then go for it! As PhoenixFortune has said, it sounds like you're an ideal candidate for the course. Obviously most universities are quite open with which subjects they will take, but I know Biology is looked on very favourably (and as I stated in my first reply to bright eyes, it will definitely help once on the course), as are English Language and Spanish, as they will help with the language/grammar aspect of things. So I think your subject choice is really strong, and you can definitely put forward a strong case in your PS as to why these subjects have helped prepare you for the course.
Work experience wise, it also sounds like you're off to a great start. As far as I'm aware it's quite unusual to get to shadow a speech therapist before you actually start the course (I know I didn't) so that's excellent, and you can really make a big feature of that and of what you learnt from that. Working with people requiring respite care is a client group an SLT may work with, so that's definitely relevant. I would say when it comes to work experience that I don't think you can have too much, so if you can find any more opportunities to work with relevant client groups then that will make your application even stronger.
To give you an idea, when I applied in 2007 I took English Lit, German and History and was predicted AAB. As for work experience I had attended a local hospital open day designed for perspective SLT students, volunteered at Brownies and did my year 10 work experience at a nursery and a special needs school. I managed to get into 4/6 unis I applied to!
As for the "you may not get a job at the end of it"- don't worry about this yet! It's true there are a limited number of jobs, but a few years ago this wasn't the case, so things can often change. Equally, I managed to get my first job a couple of weeks after graduating, so as long as you're willing to be flexible with what you want to do and where you will do it- it's definitely doable. I would just concentrate on whether you think it's something you can see yourself doing for the next 3/4 years at the moment, and if it is, don't be disheartened, just do as much as you can to secure yourself a place on the course!