3 months
But a bloke at work had an issue with his car and 6 months down the line he's £6k out of pocket as they shut up shop when the baillifs were appointed and he's still trying to get both hid car AND his money back as they have both

If they haven't done so start putting everything in writing, send them a letter explaining what you've write here and give then a timescale to sort it out you will reject the car and expect your money back

Don't be accusatory, they might want it fixed too

It's the next letter where you say you are disappointed in their unwillingness to help