They're good Universities I would say that A levels are much more important than GCSEs I know someone who applied for sussex for english as a mature student and was asked for AAA so its more about how confident you are for A levels which are far harder than GCSEs
Im always a bit skeptical about BTECs i cant help but feel universities are still prejudiced against them, I have a BTEC in public services which i got a Dis* in and it only took me 2 days to achieve whereas i know some people spend 2 years doing, that's not a criticism of the course but rather how it is administered i certainly don't think the amount of work i put in was worth 4 A*s but I wouldn't doubt that if I spent 2 years doing it, it may well be.
anyway rant about not convention qualifications aside predicted A level grades are more important and just do your best, I did alot better than I was predicted at GCSE so you may be surprised.