I don’t know where you are in the country, but Allens Performance near Nottingham have always been good for me, back in the day. https://www.allensperformance.co.uk/
Only one guy I would recommend (who did mine) and many of Classic TT guys to boot! and thats Matt Harper @ https://www.harpers-ultrasonic.com. He's not quick as he is normally really busy, but he is very thorough and there is not a lot he doesn't know about FCR's!!
Thanks for the responses. I spoke to Matt Harper this morning and will be posting the carbs off tomorrow.