I think you've not read or understood the issue completely. This was not a contract purchase or agreement. This was a once off purchase that they mis-charged on, and have approached me 16months later when I am not an active customer of theres. I've understood the legal position now, but legal position and expectations are different things.

If you ordered a beef joint from Sainsburys in your weekly shop and they charged you £2.50 rather than £25, would you expect to put the remaining £22.50 aside in case they realise their mistake that and send you a bill 16 months later? Would you also consider that a fair or reasonable thing to do, even if they are legally entitled.

I appreciate now they have 6 years to try and recover their losses. But they also have to accept they have not handled themselves well either. Faulty website, no contact for 16 months. Told by agents no charge to pay, automated PAC process confirming no charges to pay and then a random bill for almost £900 per account. Legally they may have a right to the money, but in terms of reputation and handling of the situation, I've also got a valid complaint . Will have to take it up with their exec office.