1. The minimum requirements when I applied a few years ago were a B in Chemistry and a C in one other science subject. I would therefore check the UCAS Course Search description for different courses and determine whether you will need to keep a second science subject (i.e Physics). I am unsure whether Maths counts. Failing concrete evidence from the UCAS website, I recommend you contact some school of pharmacy admissions tutors.
2. Medicine and Dentistry has a deadline of October (or used to...?). Pharmacy has the usual deadline of January (again, this used to be the deadline.. not sure if this has changed?). As a result, you can apply up until the usual UCAS deadline but I would strongly recommend applying as soon as possible. Gather as much information as you can for the UCAS process prior to the applications opening (work experience, personal details, passport numbers etc... you can even begin drafting a personal statement over the summer).
3. The playing field for pharmacy is pretty much level these days as there are no clear-cut schools which stand out above the rest. However, in my opinion, degrees from UEA, Aston, London SoP etc (and, no doubt, Durham once it settles in) will be more desirable.
4. I would recommend producing a CV and handing them into local community pharmacies. There are many pharmacists who will be willing to introduce you into the profession with a week or two in their pharmacy. Ask and you shall receive. Obtaining at least a week in a community pharmacy will boost your chances considerably.
5. All jobs in the current economic climate are saturated. So, in a word, yes... pharmacy will be saturated by the time you graduate. However, that doesn't mean you will become one of those disappointed pharmacists posting doom-and-gloom threads on forums like this one. If you excel and prove yourself a good enough candidate, there will always be a job for you. Pharmacy is still a thriving business in this country and around the world - every pharmacy needs a pharmacist. Therefore, there will always be jobs. It is just a matter of being good enough to get those jobs.