MOT Fail advice

Barmy_Army_92

Hi, 
My car [2006 mini cooper] just failed its MOT on the following;
Repair immediately (major defects):

• Offside Rear Service brake excessively fluctuating (1.2.1 (e))
• Offside Front Service brake lagging in operation (1.2.1 (d))

It is an old car so I was expecting to pay for some repair work, I was quoted £220-£360 by the garage on the day of failure. I've just taken the car down this morning, and a different mechanic has now moved the previous worse case scenario cost of £360 up to £560 on account of not knowing the job as he wasn't in on the day of the mOT, and not knowing if all the brakes would need doing repairing, and the previous mechanic who suggested the initial cost hadn't accounted for needing new sensors etc. 

As you can already probably tell; I'm not very knowledgeable about cars, what I would love to know, is 
A) What typically, actually needs repairing to fix these defects? 
Do these quotes seem reasonable? 

AdrianC

Rear could just be a slightly warped disc - discs and pads are basic routine consumables.
Front could just be a slightly sticky caliper slide - just a bit of cleaning and lubrication. While it's apart, it'd be daft not to put discs and pads on if they're getting due.

But it's not going to be straightforward to say for sure until they take it apart and have a good look. At the outside, it might need four new calipers as well as discs and pads all round...

Barmy_Army_92

Went back and said I wouldn't get the work done unless it was under the original quote price of £360, predictably came back and said that they will discount down to £360 despite needing all the brakes doing. So £360 for new pads, discs and sensors. 

Grumpy_chap

£360 seems fair for sorting the brakes.  It's an old car - there's always going to be something and this seems largely consumable items.  Another way to think of it is £360 gets you a car for a year.  Get a new car and it'll be £360 per month finance payment.

Mutton_Geoff

Brakes and tyres, always worth doing in pairs anyhow.

caprikid1

"Went back and said I wouldn't get the work done unless it was under the original quote price of £360, predictably came back and said that they will discount down to £360 despite needing all the brakes doing. So £360 for new pads, discs and sensors"
Well done , did you then get the Job done properly with all the correct parts replaced or the bare minimum to scrape an MOT ? I guess you know it's safe for a few days.