Eek, that's definitely a tough situation.
Honestly, the most likely choice is to do a Level 2 course at College which takes 1 year before proceeding onto a Level 3 course for another 2 years.
Depending on what you want to do, this is not that bad. You can easily get great grade on a BTEC at College and proceed to a great University (As long as you dont want Oxford or Cambridge).
What are the reasons for wanting to go to Sixth Form so bad?
I have been and still am at College and would choose it over Sixth Form in most circumstances. The 3 days a week mean you have plenty of time to complete any coursework as well as hold a weekend job if you want. An Extended Diploma is equivalent to 3 A Levels which is likely what you would complete at Sixth Form with Distinction* being equivalent to A/A*'s in UCAS points.