I was in the same position a year ago.
I asked Jim in Rydale - he said "we can get it done".
I went into Hein Gericke & asked the posse members lurking where they go. Fairwater garage was recomended so I went there. £15.
The bike tests are only done on a Saturday.
Tel. (029) 2055 3383.
The tester had never seen a GS before. He was in awe of it's presence. I knew the bike was fine as it had been serviced 2 days previously by Rydales. He walked around the bike, checked the lights, after consulting the manual to determine the rules for twin headlamps. Had a chat for 10 mins and he wrote out a certificate. I would imagine he has seen a lot more GSs in the last 12 months so perhaps he will be a bit more thorough.
Map Easy to find, up St Fagans Rd from Western Avenue, turn left when you see a sign for Fairwater police station.
I now live in Roath. I had the cage MOT'd in the cage only City Rd Motors in Bedford St. The chap has a Fireplace. He gets that MOT'd in the place on City Road. BGM Motorcycles, 162 City Rd, Roath. Tel. 029 2040 2800 - I've never been in there so no idea what they are like.