Small polish will end up as a full refinish/ polish to the case and bezel. It’s a bit like toiching paint up on a car, you have to get it all looking consistent.
Servicing a chrono takes approx twice as long as a 3 hander so you can expect to pay substantially more.......frankly you’re being over-optimistic if you expect it refinishing and servicing for £120!
Around £150 for the movement ( to include a new mainspring and barrel) plus £50-£60 for refinishing is a more realistic minimum.
I’m not offering, too much to do at the moment.
Paul