Have a chat with Rob ( Vintage Rob
) he's been making a living out of pretty much doing what you seek to do and in addition film company prop hire. He must have come up against all the legality and safety issues so might be able to help steer you through it. He's in Norfolk too so you could be considered in direct competition but maybe there's enough to go around in that neck of the woods. http://vintagetvandwireless.com/
Might also be worth talking to Richard at pasttimesradio
he's being making a living at if for the past 16 years. Then there's Golden Age Television
, they are pretty well known too. They all might have some tips to help steer through the inevitable minefield.
As for the legal side I used to offer a service via the main web site. Not me repairing but a directory service of engineers around the UK who could offer such services to the public, with me acting as a conduit. The implications of even being involved at that minimal level was just not worth the risk it even exposed me too. This in no small part due to modern world of litigation and no win no fee madness. No wonder I have to even be careful what is said on this forum and any advice that might endanger the ill informed should they try anything described.
One crazy world we inhabit now!