I have found the original spec for our 1985 car (B31 HWP - where are you now!) and it lists:
- Separate Wing Beading - £100
Cuprinol treatment of the ash frame was an extra £30 and underseal £45.
Sounds a lot that far back for wing beading but guess it relates to the extra cost of removing bodywork for individual spraying, then re- assembling, something that happens by default nowadays as is the ash treatment and underseal.