but GH they can't possibly know whether they will be full or not - it's not like a school where everyone puts their child in the September they turn 5 and they move up year by year until they leave age 11.
Think about the variables - firstly you want a place in 6 months time. They have no way of knowing how many vacancies they will have at that point - the turnover is generally pretty high as people usually take their babies out if they go on maternity leave, and lots of people will put their babies into local authority nurseries age 2 as they are cheaper, and the notice period is generally only 1 month. So they are not in a position to have a good idea about vacancies until a couple of months before.
Secondly supposing they have a place but you only want it from August. In the meantime another baby turns up ready to start in Feb. A childminder will charge a retainer to keep the place open for you but a nursery doesn't do that, they fill the place and trust to luck that another place will open up for your kid.
Thirdly half the people on the list will put their names down and never take up a place.
There is no way they can look into a crystal ball and say "in 6 months time we will have 12 places, and you are number 13 on the list".
But I agree talk to the manager - they can probably give you an idea about how over or under subscribed they are and whereabouts on the list you are. Bear in mind, too, that nurseries often like to give the impression of being more oversubscribed than they are to encourage you to put your name down in good time. I was lead to believe that DS's nursery was very over subscribed, and then at the last minute I found I needed an extra day a week. They fitted him it at 1 week's notice!
But don't stress too much - as I said before, I know literally dozens of parents with kids at nurseries in N London and I don't know of a single instance where they paid a deposit and didn't get offered a place. I'm sure you'll be fine.