Your local association should have this Q on their subs form when renewing, the Sec will then forward your details to Area Assoc and then on to BBKA if you wish to be a collector.
Problems can arise if you are the only one locally you can become inundated with calls then where do you put off load any swarms, one or two may be handy but if you end up with many more even 10 or more you may soon get a bit fed up if no one else can take them from you.
As a beekeeper though you can show off your collecting skills as many are fascinated of how you retreive them, this can take 10/15 mins or less or up to 3 or 4 hrs for a trickier one.
Sturdy cardboard boxe's are good 16 - 18" square or a lightweight nuc box, clean old bed sheet to lay on the ground and then wrapping sround said cardboard box. Trigger spray bootle with water or light syrup is useful, as is a cheap jacket and veil used soley for swarm collecting only. I try and reuse the same old sturd cardboard box as over time bees will leave wax residue which encourages future swarms to quickly relocate to said box and stay.