Nothing wrong with that!
I'm in South Wales, and got my letter/survey from reform a couple of weeks back, (I was expecting one bc my ex had one a week previously!).
I too wrote nearly exactly the same - 'Fuck Off Fascists' - directly under my name and address and posted it back the same day.
Hopefully so they know the wise move would be to not knock my door, lol! ✊🏴 #reform #wales #ukpol