That's BO**OKS Andy
The LAW says that they MUST replace or refund
Phone Trading Standards today
They are breaking the law and MUST be held to account
If they are under the impression that you are ignorant of your rights and they think they are "too big" for you to argue with (like banks,insurance companies etc.)
Then it's your duty to bring the LAW (hard won) to bear on them
Keep us informed please Andy, I'm sure we all really want a satisfactory conclusion for you, to this appalling saga
And would be good to know how they respond to having the LAW on their case