Good garage near North London?

Hello! We usually take our van to Mill Gap Garage in Eastbourne who are excellent, but at the moment we've been using it for work in London (Muswell Hill) and we've got a bad oil leak and a problem with the exhaust so we can't drive it back to Eastbourne... Can anyone recommend a good garage who won't rip us off in the North London area? We could drive maybe half an hour so Hertfordshire might also be ok... Any help would be much appreciated!
Thanks!