hi Simon,
Welcome to Pprune - you don't have to be mad to post here, but it helps
I'm a SE England aviator too, so my 2p is to check if you would be flying off a tarmac or grass strip.
'Tarmac or grass' is a favourite topic on pprune and each has its advantages and exponents. But for a student, trying to maintain continuity of training, a hard runway has the advantage.
You have only to look at the weather we have 'enjoyed' over the last few weeks to realise that a grass strip is now a bog.
So even if the sky is clear and blue, you wouldn't be able to do circuits as the strip would be unuseable.
Stapleford has a hard runway and near to NE London, its quite cheap I believe although awkward to get to. I don't fly from there so I'm not biased.
Whichever field you chose - and Rochester is a very nice place to fly from, enjoy yourself.
Keep us posted as to your progress, but don't get hung up on the 'how many hours did you take' thing - its not worth it.