I posted a while ago when I was struggling to get my 3rd vaccine and have been chasing it up ever since.
However, I want to go on holiday in March/April and judging from my experience of the admin involved when travelling abroad a few weeks ago I've decided that I'm having a 'booster'
The logic for this is that I may very well be asked to prove that I've had both vacs and a booster to enable me to travel and I dont much fancy my chances of explaining in French or Spanish what the difference is between 3rd vac and a booster!
I'll sort out my 4th jab next summer.