MGOOF : Modern groupset on old frame

SeaBass have quoted me £40 to Respace the frame.
The big downer is, of course, that I will have to strip the frame then rebuild the bike afterwards. >Obvious really but it hadn't occurred to me.

Stripping the frame? Hmmmmmmmmm.

At most I would have thought all they would need to do is remove the crank and chainring(s), then do their magic with this fella:

Set of forks above but same principle.
Then they'd double check frame alignment and drop out alignment too and job's done. in an hour
I'm surprised that this isn't all included for £40-£60. (Admittedly, said by the man with the wooden plank.)