I am not sure at wait list stage children are definately ranked. And even if so, being likely to accept a place if offered will push you up any rankings.
Write. Add in any extra information, BF going, direct bus route, interest in key school sport, choir etc, and ask for feedback on the likelihood of them offering a place. Be clear you would take the place if offered.
As September draws closer, what schools will not want is to offer an available place to someone who does not take it, as each time they may lose a couple of weeks and thus increase the likelihood it will not be filled.
They will probably be fairly straightforward. If they are unlikely to go to wait list they should tell you. If they think they may have to, they will be encouraging.
After that phone every two weeks. The Registrar is your new best friend. (Note, most Registrars are helpful and will understand your anxiety.) A child who will take a place if offered is a useful commodity and so it is worthwhile continuing to emphasise this. (I also suspect the schools like children with nice, reasonable and organised parents.)
Wait lists will move:
- When the deadline for acceptances passes
- When state school offers come out
- At the start of the summer term, when parents sitting on state and private offers become liable for a term's fees.
Beyond that there will be the odd place because of relocation etc. You only need one girl to drop out of somewhere like SPGS for it to trigger a cascade throughout SW London schools as various girls "trade up".
Accept the state place and also phone up a couple of 13+ co-ed preps. They lose girls at 11+ and will often have places. They go at a cracking pace through Yr 7 and so your DD would then be in pole position for an occassional place. There would be no need to apply until you know absolutely that neither the WLs nor the preferred state place will come through.
I am so glad we are almost at the end of this. All I need is DD to get a University offer.... Seriously though, your chances are good.