I usually hire motorbikes from Raceways, Surrey Quays and they treat me pretty well. Now they know me and I obviously spend enough money with them they’re more likely to give me a good deal on hiring the extras at the same time as the bike, or making sure I get one of the newer models if I’ve booked in time.
Around busy times, though, they might be fully booked, so I’ve been pointed towards Riverside Motorbike Hire. Riverside are based in Bow, just off the Blackwall Tunnel Approach (East London) so are actually a bit nearer to me by road, but not so easy to get to by public transport. They seem to be about the same price as Raceways, and a similar range of bikes. It does look like you’re able to take all their models into Europe, though, so I think I may be trying them out sometime in the future.