It would be worth checking out Hammond Hire in Coventry. Apart from Hammonds they also keep a stock of and service almost all vintage keyboards, including Rhodes, Wurlitzers, and a vast array of synths. They have recently serviced my Minimoog and Prophet 5 and both have come up great. They're real experts at what they do, and will do whatever is necessary from small fixes to completely stripping an instrument apart and rebuilding it making sure every component is in good condition! They are not the cheapest, but I guess you pay for their experience. And if you go there at any point they are normally more than happy to let you sit with a tea and play the B3s or synths for an hour or two. Just google them if you are interested.