Problem with car I bought

I think you have to give them a couple chances to fix it, and if they can't fix it after a couple tries you can demand a refund. That's the way it is here don't know if same applies in Northern Ireland with cpcc

You would think that a problem identified during warranty would still be under warranty if the garage hasn’t fixed it even after the 6 months. Otherwise they could just run down the clock. Not sure about non main dealer warranties.

I don't think the warranty comes into play when it's a matter of repeated returns with the same issue and it hasn't been resolved, If you're done with it just write to them stating you want a full refund and the car to be taken back.

Can you suggest bringing it to a local garage and they pay for the bill up to a certain amount or certain labour price per hour?

this shouldn’t be too tricky to locate and fix the problem. Coolant issues are mechanical in nature and should be easy enough track. Though could be head gasket.

"Its not their fault you decided to buy a car from another jurisdiction on the other side of the country"

The OP should be entitled to a working car or a fix. Where the car was purchased by the dealer is irrelevant. And I'm assuming the dealer paid the VRT before the OP purchased the car.

Sounds like the head gasket is gone. Loosing coolant and engine overheating, very bad luck OP. You will have a fight on your hands I'd imagine.

What year is the golf?

Apologies, I didn't realise it was bought in NI (clearly stated in the OP, I missed it), thought it was one of the cars a local dealer hadn't registered yet.

If it's the head gasket and those symptoms, there should be oil in the coolant and/or vice versa. Easily checked if you've a dipstick and oil should be visible (if present) in the coolant reservoir. Oil cooler leak could be another possible cause.

Other possibility is a previous failure (like oil cooler) which may have resulted in oil still in the cooling system and hence the overheating. Would need a flush out or two to fix.

It would have to be sitting in the red for a while. Have had overheating in cars before, multiple times and head gasket fine. But in all cases, just barely hit the red.