Bless, thanks folks
Just got back, still alive so it can't be all that bad.
Parked up next to a blue SV thou and wandered through the maze to find radiology. The receptionist at radiology said "ooh, is it raining out, we're getting a lot of bikers in today"
Despite wearing my bestest pulling pants, the radiologist was a bloke, and I don't think he was that way inclined (and I don't think I am either). Also, didn't have to take my kit off at all.
Was kinda expecting a tunnel built into a wall but as folks have said, it's just a big polo mint in the middle of the room probably only about three feet deep. There's also a good 10-12 inches either side and above your head so it doesn't feel cramped at all. In and out a few times as big whirry things do their big whirry stuff over about five minutes. Then injections to make my blood glow green or something and back in for another five minutes.
Came out with a cracking headache, but as that's one of my symptoms anway I'm not sure if there's a connection. But all in all, not half as terrifying as I feared
Fingers crossed the results are OK, didn't get to see the piccys but the radiologist confirmed I was free of wood worm