Is it possible to have the rear shock rebuilt with a new gas canister and hose, can anyone point me in the right direction? I’m UK based.

I assume you're talking about the NC30 and not the NC35, which of course doesn't have a remote 'gas canister'. The NC30 shock is rebuildable (I've had one done). There are several bike suspension specialists out there, such as KAIS, Brook,TW and K-Tech. Google them and ask their advice. I expect you'll get a few recommendations from people on here. Personally I'd go for K-Tech but I'm sure others are just as good.

Ive got a rebuilt shock on one bike the original canister has been drilled tapped and fitted with a schraeder valve for recharging and hose has been changed dont know who did job though but sure any of the places mentioned would be capable of doing so for you.

MCT will do this for you, I have had a few Honda shocks serviced, revalved and re-gassed the latest being a 1999 blade shock that had a remote reservoir similar to an NC30- there dont seem to be many that they cant work on and MCT come highly recommended. A quick google will find them and they are helpful on the phone to discuss requirements.