I think I might come across as a bit more optimistic as regards ex-polys because
a) I went to one,
b) I got a major scholarship to do the BVC and
c) quite a few people at my particular insitution have gone on to secure very good training contracts and a couple secured pupillage (not bad, especially considering te relatively small number of students who go on to the BVC).
Quite a few of my friends are planning on starting uni at around the 23/24 year old mark, so it's definitely not unheard of. Also, you may find that, ironically, it works in your favour as a 26/27 year old will be that bit more mature than a 22 year old, but without the likely 'baggage' that someone in their lates 30s and beyond might bring.
Anyway, keep us updated and best of luck.