Thanks @BunnyRuddington that's helpful. Not sure I can phase another section recovery with 2 little ones but we'll see.
The only plus point would be that there's nowhere to drive to anyway! 
How old are the other two? Would they be in Preschool or School by the time the third turned up?
Would you be able to do things like get a milkman, shopping delivery and a cleaner?
Have you got anyone who could help out? My DM is pretty useless and my DMIL's idea of helping was holding the baby while I did everything else, including waiting on her, but yours might be better? 