Ok..I know how it sounds. But hear me out!
My 10 year old is very sensible and mature for her age. She is also lazy beyond belief so I have left her at home alone for periods of time knowing there is absolutely no way she will do anything silly as that would involve moving! My 4 year old is obviously, at age 4, not so sensible, however she is a very good sleeper, and since the nightmare baby days she has not woken up, ever, once she has gone to sleep until the morning.
So I was thinking, if my 10 year old was fully briefed and left with her mobile next to her with the instructions to call me if dd2 woke up, would there be any harm in leaving them for a couple of hours once dd2 was asleep, if I was staying very local and could be back within 5 minutes? Also, my ndn, whose dd pretty much lives at our house during the day, has said that if I ever did want to go out dd1 could just give her a shout if dd2 did wake up - our back gardens are actually linked by a small gate so it wouldn't be hard for dd1 to call for her.
Am I being nuts? I am very skint and a LP and haven't been out anywhere socially for at least 4 months as I just can't afford a babysitter.