Hi Moz, it really depends what you mean by service.
generally there are 4 levels of repair that most repairers offer. I offer the following
1. Tweak - e.g a minor adjustment to sort a leak out. priced on an hourly basis
2. Thorough checkover - check all pad seating, adjust where necessary, check and adjust spring tensions where required, check all linkages,remove any double action form keys, replace cork and felt as necessary,lubricate, general wipe clean and set to good working order. £50 ish - same day service if booked in advance.
3. Service - strip the instrument of all its constituent parts, clean body bore and keywork. remove any play from keys in between their posts, clean and check all pivot/barrel screws, rod screws, clean all hinge tubing. check and adjust fitting of the crook, check the pads for wear and tear, clean and replace as required ( I include a max of 5 in the price) usually a few palm keys, low Eb, G# maybe. Re assemble, adjust and regulate linkages fitting cork and felt as necessary, lubricate the mechanism and set to good working order. £150 ish 2 days. does not include the polishing of silver instruments. any additional work eg soldering priced at an hourly rate.
4. Overhaul - as service plus, adjust/level toneholes as required, remove dents replace all cork, all felt and all pads. From around £320 depending on the condition of the instrument. 1 week
I quote firm prices once I have had the opportunity to inspect the instument - prices obviously depend on the age and condition of the instrument. And timescales dependent on availablitiy of spares/pads etc.
I hope this is of some help.