You're probably looking North London then mate. the clubs i know in East London play either in the Essex league (which means a trip to the countryside every other weekend) or play a relatively low standard (Walthamstow CC as an example of the former, and London Fields CC as one of the latter). You could try Tower Hamlets CC but I don't know them that well. I think they play division 1 Middlesex Championship.
North London has a fair few clubs (I play for Alexandra Park CC. Takes me 30 mins on public transport from Walthamstow). There's also North London CC, Crouch End CC, Highgate CC, North Middlesex CC, Southgate CC & Edmonton CC, all of whom have teams playing at a respectable standard. There are probably more but that's all i can think if for now.