DD has been offered the place but too far from us. I identified the school which is in different borough which would be ideal in terms of school runs - and also it is a very good school. there is a huge waiting list. I have made decision to move nearer the desired school... so is it better that I move in summer ( find the place to buy) - will it give me more chance to get a place before september rather than applying later after summer fro In-year admissions? Just think if there are people who are holding on to private and state school places - so maybe in august will reject state school places - so maybe in august there will be a good chance for people who are on the waiting list?
If you move house to live closer to the new school (and if you apply for a place there once your address is confirmed) you will be higher up the waiting list than people who live further away than you do. If you move very close to the new school, you might be placed very near the top of the list with perhaps only siblings above you.
However, it might be too late. A lot of movement on the lists tends to happen now not in August. That's not to say they'll be no movement over the summer but April/May is the time people accept or decline offers so the first wave of vacancies will be coming up any time now. Unless you know something about this school that leads you to believe dozens of people are hanging onto a place until the last moment, I would be really wary about relying on waiting list movement let alone going to all the hassle and expense of moving house for what will be a long shot. Any vacancies the school has might be long gone by the time you move.
Have you explored options nearer home. Where are you on the waiting lists for the schools you originally applied for. Might it be possible you'll get an offer from one of them?
I don't want to sound negative but unless you know the school has lots of drop-outs or unless you are prepared to perhaps wait years for a vacancy. I think your plan sounds very risky.