I'm familiar with the options, firstly when are you looking for as Esher College has already closed and offered places for September 24, if you want Sept 25 you need to register by end of Sept 24.
6th form colleges include Richmond College, Kingston College, Feltham College and Esher College.
Schools with 6th forms include Orleans Park, Teddington school, Greycourt, Christs. Some have very few spaces for non siblings ie Orleans Park.
Richard Reynolds's is catholic but the 6th form often has spaces, check out the entry requirements.
Some schools like Hampton High and Thamesmead don't have a sixth form and have formal links to 6th form colleges like Esher guaranteeing entry.
I can understand why there isn't a list as it wouldn't be much help as the admissions criteria of each school is different and then different again for the colleges that aren't all in borough plus as I've said some schools have 6th forms but virtually no spaces for new admissions at 6th form.