It is, but it gets considerably shitter if you can't do stairs.
My mate next door at my Woolwich workshop uses an e-chair, and his life has been considerably improved by the new segregated bike lanes that head into Greenwich. Sadly alot of the stations along here are not step free
I realise this is going to be an unpopular position, but I actually think the public transport system in London is pretty good. Remarkable in fact.