I would make a complaint through the motor ombudsman.
If you can provide sufficient evidence of the fact that it is a common fault to the model, it might lead to a vehicle recall.
Besides gathering evidence, clearly the fault has the potential to result in a serious accident should it occur as you are turning across fast oncoming traffic (or other such similar situation).
Also check-out other vehicle recalls, to see if this type of vehicle fault has resulted in a recall.
The ombudsman may be able to help you obtain redress from the garage (if they expect you to contribute to the repair costs) – but normally you will have to have exhausted the garage’s complaints procedures before the ombudsman will adjudicate the matter.
https://www.themotorombudsman.org/consumers