WD40 isn't a great penetrating oil. Either use PlusGas or the graphite type of penetrating oil (Toolstation sell no-brand stuff fairly cheap). Although to be frank, I'm not 100% sure that penetrating oil will do much good in this case.

Neither do I think the small amount of heat available from a blowlamp would work given the huge heat sink effect of frame, swingarm etc. Possibly a gas welding torch but it is a bit medieval in that location.

I assume the pivot bolt nut can be removed but the bolt itself is seized in and won't rotate?

If that's the case I would apply a long breaker bar to the end of the bolt; if that doesn't work then an air driven impact gun - sometimes called a "rattle gun". The compressor and guns you can get from Lidl or Aldi are not usually man enough for this kind of job but you may be lucky if you can borrow one.

If you haven't got a man enough air impact gun, reassemble the bike and take a trip to one of the independent tyre fitting places (don't bother with Kwik Fit and their ilk - robbing B'strds).

Ask the friendly tyre fitter to apply one of their impact sockets and gun to loosen it off (remove the nut first, then refit when the bolt is loose).

This may cost you a couple of pints for the fitter but will be easier and less destructive.

It's what I used to do when I was faced with a stuck 36mm hub nut on VW campers - absolute sods....

__________________
Simon

Brighton, UK