You've asked so here goes.
Generalities but hopefully help you make a more informed decision.
Brake replacements are a standard job that any garage set up should regard as bread and butter and not load prices for unknowns/contingencies.
In that respect I would expect very similar labour times plus the parts price.
First part is the labour price and there is a significant difference across the industry.
Main Dealers (Doesn't matter which make) are most expensive generally charging around 90 pounds per hour
National Franchises (Like Kwik Fit) second around 50 quid/hour
Smaller garages from around 40 to maybe as high as 60/hour.
So ask em, how many hours and how much per hour ?
If someone is telling you twice as many hours, chances are they are either trying to rip off a naive customer or are just plucking a figure out of the air.
The national franchises and main dealers work from "standard" hours so will usually give a better idea of the time it should take.
Parts pricing can also vary. Again, main dealers will be priciest. Then franchises, then independants. Again, the latter may be trying it on so ask the parts price.
You can price up the normal retail price yourself by going to a spares shop and asking for prices..just give them your reg number and they'll sort em out for you, check on
for pricing, use an online supplier like Europarts, again, just pop your reg number in and you'll get all the info you need.
Espect the parts price to be around retail except at main dealers who will be significantly more.
Garages buy at trade and sell at retail. Good ones at less then retail, poor ones at more. Don't begrudge em a profit margin, do object if they are trying it on.
People that come out with spurious reasons for the cost are ripping you off or just guessing. ABS rings are a standard on many modern cars if not all. Yes, it means the discs are a little more expensive but not over 400 hundred quid.
Do ask what make the parts are and check the make. There are cheap knock offs/fakes and can be dangerous. Too cheap for parts, be suspicious. It's someones life with brake failure.
Don't be afraid to negotiate. Franchises will usually knock off 10% without hesitation if the price is queried, can be pushed to 15%.
Independants tend to work on tighter margins but don't ask, don't get, even a tenner or a discount for cash adds up.
Knowledge is power. So do your homework and shop around. Nothing wrong with taking the low price just do it with your eyes open.
Final, check it is a quote, not an estimate. Quotes are firm and price you pay is what is quoted. Estimates are that and final price can vary. Less honest places will find "problems" during the job and load the estimate.
Problems can occur but an honest place will phone you, if say they find a leaky caliper, and tell you before going ahead with replacing it.