I would ask them. You can say they are in breach of contract pursuant to the Consumer Rights Act 2015 by failing to act with all reasonable skill and care.
I would also call Kwik Fit Head Office on: 0800 757677
They should be able to resolve it.
Or pay on credit card to get the car back and then sue for the costs.
You need to write and set out your losses and request a refund within 14 days or say will go to Court within 14 days. You should make sure you send this signed delivery and keep a copy.
If they do not refund you then you can issue proceedings in the County Court. You can either do this online at: www.moneyclaim.gov.uk or by completing form N1 http://s3-eu-west-1.amazonaws.com/hmctsformfinder/n1-eng.pdf and take it to your local County Court.
The Court will then issue a claim which a copy will be sent to the Defendant who will have a limited time to defend it, if not you can enter Judgment and enforce.
If the claim is for £10,000 or less it will be a small claim so you will not need legal representation. Over this value you would need representation for trial.
But if you call Head Office I am sure they can sort it for you.
Can I clarify anything for you about this today please?
If not, I would appreciate a 5 star rating for my answer. Thanks!