I'm Ian Vincent Knowles, born in Aylesbury Royal Bucks Hospital on 5th February 1985 and I want to find out if my parents who brought me up are my biological parents?

Your 24... can you ask them? Or get your birth cert?

I really don't know much about this,but it would seem like the first logical step.

I'm Ian Vincent Knowles, born in Aylesbury Royal Bucks Hospital on 5th February 1985 and I want to find out if my parents who brought me up are my biological parents?

Yes I have but there's something that don't add up,when I asked them,it was the way they responded,it just seemed suspicious

Have you seen your birth cert?

Please explain why you have doubts and what "does not add up"
And of course a simple home DNA test, while not OK for court would tell you for sure