Well i am a registered childminder, i lived in a first floor flat (housing association) when i became registered with no garden. Infact the fact we had no garden actually meant we were out more doing constructive things then just letting them run free in the garden (i know LOTS of childminders do that for too long) its nice to have a garden(i do now) but it wasn't essential,i mean you say about thunder and rain but who plays in the garden when its raining or thundering?
As for the noise,my neighbours were nice for about a year and then they just got fed up with the early arrival of my (NOT VERY QUIET) parents and children and complained so much to the housing association that they threatened to take me to court for breach of tenancy as my business was causing a nuisence!
Anyway,we needed my income and so decided to give the flat up and rent a house privately (had waited 5 years for the flat!!) but we had no quality of live with the complaints and walking on egg shells.
It wasn't fair really and part of me wanted to let them take me to court and fight it but it was so un pleasent i just needed out.
The thing is,we had children and the neighbour would of had to just put up if we couldn't afford to move but i wasnt happy knowing we were making his life unhappy. So it is doable,but you need to be certain the flat you move into is well soundproofed and you have shown ofsted what facilities there are nearby to ensure you go out such as parks,library,playgroups etc.
All the parents who took me on just wanted their child safe and stimulated and thats what they got. and i know i was chosen over some with gardens because of what i offered and my personality..i kept all the original mindee's when moving.
good luck!