CATS - Cranfield Aviation Training School do a free PPL groundschool course online, you could try that.
I did CPL groundschool with them some years ago and was reasonably content; I've not used the PPL material but not heard any complaints about it either.
Apart from that, given the dreadful weather in the UK this week, I'd have thought that pretty much any local flying instructor would have no problem helping you out without disrupting his flying programme.
G