You can just swap - I did last year. If by any chance your current group is not on express weigh (the computerised system) then it may be beneficial to ask for your record sheet, and if you've got a countdown - you'll need the vouchers too). If you're already on express weigh - then just go for it.
People change groups for all sorts of reasons - work/family gets in the way, whatever. but you can weigh at any group once you join.
.