I would like to swap to a levels but I stupidly continued my btec course into 2nd year and now wont be able to get into uni in a course I want
Would I be able to do a levels next year? or will I be declided due to funding?
You should be able to get into adult colleges that offer A Levels to 18+, but these are difficult to find. You should then look into Advanced Learner's Loan for these if your application is successful (these aren't free, but you get funding for them).
The alternative would be to do A Levels privately or through online colleges, but you won't have access to any funding for these as far as I know.
Which specific degree do you want to do, or rather what line of work do you intend to do? You might be able to get around the BTEC/A Level issue if you pick the degree you need at a different uni or supplement it with specific A Level(s)