Thank you for your responses. Appreciate all of them. I have looked into all the colleges in the whole of London for options. Boy this is tough and yes compromises all the way.
Home tutoring not an option as the parents are limited in funds but more importantly it's the other hours they are concerned about re monitoring, getting up to mischief, completing homework etc. as they both work long shifts.
William Morris Sixth Form, Hammersmith offers GCSEs - but most of their pupils already come from 3 local schools or local catchment area (Hammersmith Borough) so may not have a chance (as live in Ealing Borough). Apparently they hold a few places back for those schools in case pupils fail/need to retake GCSEs so although they may say they have places they may not really be free.
Richmond Adult Community College (Richmond Borough) has GCSEs but no French so we would need to find a tutor or another college to do that separately (French is a must as she must be so much more advanced than some as it's her first language).
Twickenham Academy & Richmond College could be possibilities but have very strict catchment criteria and oversubscribed (plus do not do French).
If anyone knows anything about these Colleges (experience/background/details) it would be really appreciated to hear some feedback as we are going in blind. Tried to call all places but on holidays.
Many thanks.