Welcome to the forum.
An internet search will reveal many UK sources.
NickG, one of our master tuners, has extensive knowledge of these and may be the best person to ask re size / crush etc.
One of the problems likely encountered could well be less than perfect cylinders, though. Especially with the Meteor. Some tuners have had much success using the 25mm Weihrauch parachute synthetic seal in the Meteor. I have fond memories of shooting a superb example thus tuned by "Shed tuner". Hopefully he'll be along with details / link to a previous thread.