This was another advisory from last year, so I've replaced them this morning. I was surprised that the wishbones sprang back up of their own accord with some force once I'd got the balljoint out. Is that normal? I also have to replace one of the CV boots, does this springiness in the wishbone make that quite difficult? Thanks for tips.

Yes that's what you would expect in fact if they didn't I'd be more concerned also you're fighting the anti-roll bar which is trying to do its job you're pulling one side down as the other side is up On the subject of CV boot you three choices a split one which means you don't have to take everything off the car remove the old one slip this one on and glue it together quick fix but not one I would use personally option 2 stretchy can be bought on eBay for pennies make sure you get one with a long cone to fit it, final option remove CV joint from shaft well worth avoiding unless you're confident

I don't think I have an anti roll bar. I suspect the wishbones are stuck to the rubber bushes. Should I spray them with some penetrating oil?

I will look at the stretchy cv boot option - thanks for the tips.

not on the rubber, When you've got the bolt off the ball joint remove it completely  put some penetrating oil around that area find a suitable long piece of wood or steel bar jam it under the inner wing and push down on wishbone this should release the ball joint and allow you to lift the suspension strut away it's not the tape joint you would find on a track rod end which can be very difficult to remove you won't need to take it off on this occasion.It's also recommended you replace the nut and washer on the drive shaft you will need a 30 mm  socket for that. I don't on my own car and never have done (Might regret it one day)