Good on ya gazzebo
The problem is with interpretation with trucks that are the age of ours...if someone was instructed to change everything that is worn, then we would end up with a new truck and a bill that would buy a Cayenne. My thoughts are with older vehicles that the owner should know what is wrong with the truck prior to putting it into the garage...so you should be telling them what you want changing and have an idea of how long it will take and the labour costs associated with that.
There should be no surprises as you should know your truck and what needs doing and what can be left to be sorted later on.
For example...If I blindly stuck my 2.8lwb in and told the garage to "sort the brakes"...then they would change both front calipers as they sometimes stick when the pads are getting low, they would change the flexy's as a precaution, and probably all the brake lines underneath as they have a bit of corrosion in places. This might mean it also needs a new bias valve as the brake lines would probably not want to come undone from it. Bingo...£1200 bill!
Most garages arent interested in doing half a job, and realise that they have a responsibility for peoples safety, so wont second chance anything. If its corroded then it could fail, or could break during disassembly/reassembly, so these components are going to priced into the job.
Hence we get stories like the 205 up the thread, where a replacement seal might have got the brakes working, but paying someone to strip and replace seals sooner than replacing a mastercylinder will reduce the parts bill and increase the labour bill...so no win, and in honestly I would sooner have the new part and pay less labour, sooner than a repaired part for the same money. But then what were the condition of the rest of the brakes/lines like? Might be that you were happy with them, but would someone "who knows better" be happy for you to drive on them, potentially risking your life and others, and leaving them selves wide open for legal proceedings and prosecutions should something else fail...and the driver/owner then claimed complete ignorance with their No-win-no-fee lawyer.
Long and short of it is...Know your vehicle, know what it needs before you ask, research cost beforehand, understand the garages responsibilities, and then get a written quote...then you will get no surprises.
Try and use a garage/mechanic that is recommended, cost is largely unimportant, a mechanic you can trust, understand and who understands your vehicle is a great find and one to hold onto and support.
Personally speaking my local Kwikfits are great, really helpful and I have never had a problem with them at all.