A Levels + H&SC course simultaneously? Mature student in need of help please!

Greetings interwebs!
I wish to eventually study Psychology at Uni. Currently looking for 6th form colleges to take it at A Level. I hope you can help to answer my questions that are stressing me out at the moment.

As a mature student who completed A Levels in 2011, will I still be eligible to apply for the same undergraduate Psychology courses as other students as long as I complete the A Level before I apply?

Is it common to do A Level part-time (i.e. under 3) alongside a different course like a BTEC in H&SC? Can anyone confirm if doing a H&SC course on top of A Level will make me a more desirable applicant? I don't have exp. with BTEC courses personally but don't they offer practical experience? What other courses can I take that offer practical experience? After contacting 6th form colleges, some don't even allow me to take both and require a minimum of 3 Alevels which I have already been through the pains of!

Because I'm a mature student returning to study, what else can I do to add to my application?

Many thanks.
Advice is hugely appreciated.

It would be best to ask universities how they feel about second sittings of a levels. If you already have 3 a levels then i m not sure a btec would make you look more desirable. what a levels did you study in 2011?