Hi - I also have done the GDL as a mature student, and thought I would let you know my thoughts on your situation.
The GDL is intense, hard-work and TBH with you, not all that much fun. I agree that the GDL won't really give you an idea of what it is like to work within law, but it IS interesting and inspiring in parts. But very hard work and academic, as far as it goes - it's basically a giant, difficult memory test.
You haven't mentioned whether you would consider a solicitor route - it is not as competitive as the bar.
The bar is more competitive than you can possibly imagine to get into - I would suggest that you find out the names of some of the top Chambers near where you are or where you might want to go, look up the profiles of their mini pupils and see how you measure up - gives you an idea of what you are up against.
Your 2.2 will be an obstacle. Your mitigation circs should be considered against that. There are other routes to qualifying as a sol other than a training contract (which is like the pupillage) which can help to 'get round' the 2.2.
If you are serious about law, it is a good idea to spend a year getting some experience out in the real world somehow - also, unless you really like being a student (I don't much) then you will be doing back to back university!! Either way, you will absolutely definitely need a stack of work ex/pro bono stuff to get on in law - it is just expected for the majority of students - although I do get the impression that the v elite applicants can get away with not having any - personally, I think it is a very good idea with law to try and work out if it is for you or not before you get involved with it - because for many people, it turns out they hate law after all, once they finish studying it (especially it seems, if they do it because their parents want them to!!)
So, your questions...
1, If I don't do the GDL now and spend time trying to gain experience, how long should I do this for. A year perhaps, as further work experience can surely be gained during the two years that will be spent on the GDL and BPTC?
Well, if you do more long-term exp you get different benefits. Speaking now from my position, i suggest paid work might be more helpful but ideally a mix of paid and voluntary work. You could do something every two weeks for one day - it is possible to arrange. You don't get a whole load of spare time on the GDL, so you have to work out experiences that fit around the timetable and your own life - possible but difficult.
2, Given that I am a non-law graduate who is not enrolled in any legal training how would I go about getting work experience with any law firms or shadow barristers?
This might sound a bit presumptious and it is no doubt, but ask your dad! he obviously wants you to do law enough to chuck quite a lot of money at it - my guess is he might know some people - other than that, there are lots of charities connected with legal things, Citizens Advice, you can find some court shadowing schemes in some places, you can get yourself along to observe in court - you can thing sideways around this - any legal type of environment is fine - also worth saying, that paid work is also seen as valuable experience no matter what it is - dont worry about your age BTW wont be aproblem.
3.Even if I do gain some experience, will the fact that I have not really considered steps to gain experience until now count against me, or is it okay not to have always wanted to be a lawyer.
It is all fine, people understand that you may have second thoughts about a legal career - so that this informs your thinking is OK, it makes sense - you just have to be able to explain why law now for you - why law? is what you get asked all the time
Finally, assuming that I do spend a year gaining some experience and knowledge, and develop the required passion do you think this is a wise career path if I really want to do it, or should I quit now before the passion sets in, given the low chances of me making it?
It is totally your thing - I think, do a shed load more research into the bar before you go down that route - everyone has a low chance of making it as a barrister and a slightly higher chance of making it as a sol. Try and talk to some barristers some how for advice.
Thank you so much for your replies. I honestly thought when I posted this thread that I was going to get trolled by 15/16 year olds who think their GCSE predictions mean they are guaranteed an first from Oxbrdige, telling me I should apply for the first available cleaning position.