Riva:
Any particular reason for wanting ESP8266 modules (apart from cheapness)?
I would normally think of using something like a mesh network with NRF24L01+ modules for a job like this but a quick google shows people have used ESP8266 mesh networks
'mesh networks' that's the keyword I'm looking for. I just did a small research about it, and it seems to suit my needing.
I'll read more about this tomorrow and then look forward to get into it on the weekend.
Cheers