Thank you, I sincerely appreciate your reply.

The garage we took it to yesterday that couldn't find the fault said there were several new components in the engine that looked like the previous owners had tried to also figure out the problem but never did.

I've booked it into one more garage tomorrow who again is going to look over it for free but if they can't narrow down the issue we may pay to take it to the ford garage.

The car is in reasonable condition and we just fixed the rear suspensions, 2 new tyres, etc. so if we could manage to sort out the engine light realatively cheap then we should probably keep the car which seems like that would be our best bet financially.

If it can't be fixed looks like we may just need to trade it in and take a loss or go the auction route again but likely it would just go for what we paid for it.

I'm new to the country so I have zero experiences buying cars from a dealership here but what are the odds a dealership would give me the quoted trade in value plus knock some off the sticker price of a car we would want to buy?

If it's the engine management light (a yellow light) then you can just keep on running it until it goes terminally wrong. Which could be several years away.

Its going into limp mode though. Not very reliable or safe.

Sounds to me like the OP has bought a problem car, one someone's tried to have a go at fixing and failed, they always go to auctions as the buyer doesn't get a chance to test it. That's why they're cheap.

First thing I'd do is get a proper Ford diagnostic from a Ford specialist (not a dealer or "fix anything" garage with a generic code reader). Or cut your losses and get rid like the previous owner did.

No, it is only an advisory.

As long as the car passes the emissions test, then it's good to go.

If an engine management light is on--isn't that an MOT failure?

Thats what I think and the light only comes on if it's import (some faults don't trigger it) and if it's on there must be a code.

I suspect the issue might be outside of the ECU and often basic test kit only checks the ECU. So maybe a proper Ford dealer is your best bet.