This latest dispute is apparently concerned with bank holiday working. The FBU wants firefighters to continue with restricted working hours on 8 public holidays, whereas the government [quite rightly] wants them to work a normal shift since they are being paid double time and getting an additional day's holiday as time in lieu.
The FBU has stalled 2 pay rises totalling 7.7% in the past 8 months, and is now calling for a strike because they baulk at the idea of going to work on double pay. I sincerely hope that the British public shows no sympathy with their 'cause' this time around.