Perfect! Thank you Kevin, thats exactly the way I'm going to go using the small claims court.
Also, I'm in Scotland (different legal system) so they would need different legal advice.
I've already told them my costs for 8 months, including depreciation on the MG5 for the 8 months and £250/month for replacement car (I bought a replacement car). The total comes to the limit of small claims court £5k. They do not dispute the facts - just say they have no liability to compensate. But they already offered £500 (subsequently withdrawn) and they approved a loan car but it was never delivered because they could not agree cost with the distributer.
I'm happy to go forward with that, and thanks again for great advice.