Hi Simon, There is no way tyres in that state are safe to drive, believe me I am in a position to know! I think I need to explain something given your situation. I was informed by text that all four of my tyres were split (with accompanying photographs) so I used the courtesy car Audi had supplied to cover me for the vehicle service and went to my local tyre discounter to see what he could offer. He could do Pirelli P-Zeroes for £250 each (mine is also a black edition with 21" wheels) BUT in common with a lot of tyre suppliers he works through a discounting agent and could not therefore raise the complaint regarding my Dunlops as this can only be done through a Dunlop/Goodyear agent.
Obviously with four deeply split tyres the car was undriveable so I had little choice but to use Audi Birmingham to replace the tyres, however, whilst Audi are not Dunlop/Goodyear agents BMTR (their supplier) is and I could therefore access the complaint process. As I said in a previous post I replaced the tyres with Continentals and managed to get Audi to supply them at £268 each (they couldn't get anywhere near the Pirelli price I had been quoted but the Continentals and access to the complaint system seemed like a good plan!).
Audi are absolutely correct in that they are not responsible for the tyre issues but as "a loyal customer" (you went there for the MOT after all) you are seeking their support to raise a complaint to Dunlop through BMTR. This implies Audi/BMTR will have to supply the replacement tyres but, if they are willing to assist, and they should be, then it might even be worth haggling over the tyres' price as well.
Sorry for the length of this diatribe - just trying to help! Good luck.
Regards, Mike