I know that the current Weissman boilers are ready for 10% hydrogen (or at least plenty above the target that we'll never hit for adding hydrogen to our gas supply and I would recommend them.
PCB plus labour is probably going to hit £700 notes because they are often needlessly and ridiculously...
Oh the fun I miss when I don't check NSC.
Obviously the ops question is a "how long is a piece of string" thing.
Simmo as ever is both reasonably accurate and a little rude ;).
FWIW I would be anxious about any boiler retailing at much under a grand, and wouldn't expect change out of £500 to...