You'll probably get much better support on the Access to HE course (even compared to taking A levels at school), because you'll also be taught study and career skills. There's more financial support for Access students which might be a factor
Most universities will accept Access to HE (and BTEC qualifications) - yes, even for some medicine courses! It can sometimes be tricky working out the equivalent scores/grades needed.
(I'm in NI and the system is a little different here - I think it's more accepted by GB unis.)
In NI, the Access qualifications have a limited timeframe for use to apply to university, but I've not heard of anyone being refused on these grounds. (This might also not be the case in GB.)
You're best bet is to contact the colleges and get more info from them, and also check with any unis/courses you're considering.