Hi Marky,
I'm a site owner in Edinburgh and we, along with all other UKPSF registered sites have been advised not to fill the general publics Tanks, whether it be Co2 or indeed Air. However, we as a site will allow people to use their own kit, providing it has gone over the chrono and checked. Also, we will allow you to use one of our tanks for the duration of your play then we take it back, rendering the marker useless without co2.
Sid