Sorry I don't know the answer but the same happened to mine & I'm interested to know the answer too.

its a response to being nibbled. its similar to a gall. prune it out and hopefully wont happen again next year.

I note you say 'all my fuchsias' - if that means several and they're all like this, it may well be fuchsia gall mite. If its just the one plant, might just be feeding damage...

thank you for your responses ... Yes it is all of them and I have many .. But I also have a friend who live 2 miles from me and the same has happened to hers ? There's also an orange either fungus, rust or egg type powder in patches on many of the leaves .. I can't tell which of the above it is .. Any clues ? Thanks again x

sounds more like a gall mite then. can you add another photo with the orange stuff on it. is on the top or lower surface of the leaf?

Definitely gall mite be careful how you dispose of them very contagious difficult to treat.
What area are you this is spreading across the country if you want moor information have a look at Friends Foes Diseases on Facebook lots of information on Fuchsias.

If it is Fuchsia gall mite, there's no treatment and the plants should be destroyed - more info in the link below

https://www.rhs.org.uk/advice/profile?PID=512