Castles, beware. The Harrodian is small, has a junior school and really appeals to a significant number looking for something not hot-house.
Irisha is right. A 13+ prep provides a good back up and time to think. Add Newton Prep to your list. Its easily reachable by train from quite large areas on SW London.
I would also email Registrars of a number of schools you might consider, saying you plan to reutrn to the UK, and that you realise you have missed 11+ deadlines. Say your daughter has been educated in the French system but is bright (top thrid of her class or whatever) and should be able to transfer to the UK system relatively easily. If there is any chance of a place you can come over in February.
Then wait till the 11+ deadlines are over. One or two schools will have got it wrong, and will be going through their wait lists faster than expected. I am almost certain that if you spread your net wide enough, something will come up, either soon after the deadline for state school acceptances, or at the start of the summer term, when people stand to lose a terms fees. Reshuffleing then goes on through the summer. One person relocates, frees up a place at, say, SPGS, which then frees up a place at G&L, which in turn frees up a place somewhere else. Registrars will only know how their wait lists stand after the state school acceptance deadline. Ones who are in danger of running out of wait list will be encouraging. As long as your daughter fits within their academic range, they will be interested in adding her to their wait list. An additonal child is pure profit, plus fillng a late place with someone who does not have one offers more chance of acceptance than approaching someone who has paid a deposit, or bought uniform, elsewhere.
I would not mention KGS. Just say you are a returning expatriate. My guess is that you should be OK for Surbiton, which is used by a lot of people as a fall back and so will have more movement. It has also recently expanded. Girls there that DD knows seem to be happy and they seem to have girls from across the academic range. However you may be surprised at what does come up. I know people who have got last minute places at JAGS, Ibstock, and KGS to name but three. None obviously heading for the top half of the year group academically.