I moved to amersham 2 weeks ago and had the same problem. I have 2 boys, one aged 4 and the other is 2and a half. They both went to nursery in London but I could not find anywhere in amersham with availability. I ended up having to get a nanny (as I work Monday-wed). I have got a place in September at woodlands nursery for my youngest and Luke (my eldest) will be starting school then.
I am up for meeting up when you settle in as I need some local mum friends too.
I never saw your response (not quite got the hang of this site yet). My little boy has now just started Woodlands - seems to be enjoying it. If you still fancy meeting for a coffee/play do let me know (I am not sure how to send you a pm).