NCT Car can't be driven.

Did the ‘whole new exhaust’ include a catalytic converter? If so it will be very hard to make it pass an NCT.

OP failed dangerously on rust so should have towed it away from the centre. Obviously nobody does this tho.

It was no worse leaving than it was getting there. And often driven dangerously for last few thousand Kms since it was due its last service.

Ideally they would impound dangerous cars but that's beyond them.

driven my car with the bold boy sticker on the window, was trying slicks out for a while, wouldnt recommend them, straight to the tyre garage, job done....

You just take the sticker off the window and drive off, its not up to the NCT to enforce the law.

Sorry that this happened to you. It’s not ideal, but a near 20 year old Yaris really isn’t worth putting any money into. Used car prices have dropped in the last few months so you should be able to get something else. It’s a pity you’re out of pocket for the tyres and exhaust, it’s a tough situation but you’ll just have to write that money off.

as far as I’m aware the NCT testers don’t touch anything under a car, I don’t think they’re allowed use screwdrivers or any other tool, everything is visual.

This explains the ‘corroded brake lines’ racket when a bit of dirt is described as ‘advanced corrosion’ . I failed on this and a mechanic told me he had to replace a good as new brake line because of this scam, happens all the time he told me too.

Ye, that's probably beyond econimic repair unless you're DIYing it. I'd throw it up on Donedeal/Adverts for a few 100 listing all the recent work and let it off, chances are you'd get more doing that than scrap value.

Cut your losses and put any money you'd spend on repairs towards another car.

it all depends on the level of rust to be honest. one hole in anything is enough to fail, and is regarded as Extensive corrosion. depending on extent and accessabiluty, it could be a very quick and cheap repair at a local independent. Not so sure on the 02, could be a MAF sensor or similar, especially if you have had a full exhaust system incl. catalytic converter

Did you buy private or from a dealer? If from a dealer bring it back and demand your money back as they sold you a dangerously defective vehicle.

Not true at all. Car had a valid NCT at the time of sale and was deemed roadworthy.

OP can’t prove the car was defective at the time of sale.

Google "nct welding repairs" get a price for the Job but ask them to check what else might need welding for the next test. That will guide you.

The emissions could be a bigger problem, you got the exhaust replaced, is there a catalytic filer or was it chopped out. They aren't cheap.

My rule of thumb is that it's worth it if you keep the car 6 months and the cost of the work is less than the cost of 6 months repayments if you bought another car.

From the sound of it you should be shopping for a new car.