@SickOfTheMansplainers
That sounds extortionate! It is proving it though.
We had a Vauxhall astra 7 or 8 years ago that was only 4 years old at the time, and it failed the MOT, and the OFFICIAL vauxhall garage said it needed £750 spending on it to put it through the MOT. A couple of similar thing happened at other times too (around 6-7 years back...with 2 other BIG companies - one of them kwik fit.)
We asked them to put 2 new tyres on, and they made us believe (at the time) that we needed £450 worth of exhaust and brake pad work doing... (In addition to the £100 worth of tyres.) We let them do it and we paid for it. We took them at their word that we were driving a death trap with these repairs that needed doing.... What could we do? We have to believe them right? They wouldn't lie right? The more we thought about it over the months after, the more we thought we were ripped off. But, as I said, it's proving it.
A similar thing happened to my brother - as what has happened to you - with kwikfit 3 years ago. 4 year old car, took £800 of repairs to pass the MOT. It was a Ford focus (and mine was a vauxhall astra) not fucking Rolls Royces!!! 
I would be very unhappy with that bill and would question it, and I wish I had 7 or 8 years ago. I know this is no help to you right now, but I would never use a big company any more (for car repairs and MOTs...) We now use a company run by 2 brothers and 2 sisters, 3 miles from us. Our 10 year old car (corsa) has passed the MOT twice, with no money needing spending, except 2 new windscreen wipers.
We realised several years ago that we had been massively ripped off several times. It won't happen again. Try to find a small, family-run garage if you can; much better, don't rip you off, and won't sabotage anything to make you have to come back (which I am convinced one BIG company garage did to us once or twice!)
I hate kwik fit with a passion. Local one ripped my granny off a couple of years ago - £1400 for a handbrake cable, brake pads, one tyre and a 'service'. We got the money back and the manager was sacked but I wouldn't go near them again.
I believe this 100%.