The prospect of a nice MK1 80 for sale in .177 should have the BBS masses rushing to their PC's to say "yes please".
My own 80 is a mk1 and was orginally .22 but donkeys years ago I swapped barrels with a .177 80, also mk1. It runs around 790 fps with Superdome, god knows what it would do with a .22 barrel back on it.
I used to try to get the .177 version if I was buying a rifle but to be quite honest I doesn't bother me now if its .22 or .177. I only shoot in the garden or at my local rimfire club (25 yard max) so a flat trajectory is not an issue. If I were to hunt at longer ranges, do HFT or want a smaller rifle/pistol then .177 is the choice, but if its a sporter I am not fussed.
I even bought a .177 35 barrel off my local dealer to fit to my .22 35K (brand new £40 how could I say no) and have'nt bothered to fit it.
Keep your 85K as a .22 and enjoy.