heya, I think its the norm for sixth forms and colleges to require a b at least for the course (some colleges/6th forms should take the candidates individual circumstances into consideration though - beg them if necessary)- it may not be for the a level but i guessed it was all down to uni entrance since when i was looking out of interest many courses require b in maths.
I'm located in the North of England - I can't give away too much information on here about me bc I know a couple of people on tsr , and my a level subjects make me easily identifyable on here due to them being an unusual combination
HOWEVER, i did go to a 6th form college which was SO RELUCTANT to let me in also due to my `okayish` gcses
(and the head of 6th form was/is a witch).
in college i started doing 4 A levels (not science ones) and then droppped english lit, bc it was difficult for me, and juggling gcse maths at the same time (it didn't help the people i was with in class were in the top set and i was in a low middle set, which sort of affected my confidence. 2 of the aS levels were coursework based (one was health and social care - that may be worth looking into because we could do placements with that as work experience and it was so fun - the other aS level is one of the new spec a levels.
I had to do gcse maths again bc i was 3 marks off a C, so basically i was sitting in a class on wednesday afternoon (free afternoon), with people who'd got lower than me (so i was sitting in a room doing stuff i already knew), they were friendly though and we had a laugh and joke too.
on GCSE results day, they'll be a guidance person you can hopefully talk to about your grades and options whatever u get who can guide you in the right direction. Do you know anyone who's working in the field you want to go in, like any brothers/sisters/cousins/family members/friends who could perhaps guide you also? that would help
also you could have a look at uni courses on the web to see what is needed which may help put your mind at ease? even though i don't plan on going to uni there was a wide range of courses available to you
take care