Result!
Got confirmation today that he'll accept £2500 for full and final payment. That'll close the account and release us to move on thankfully. It's been a stressful time but we've effectively got a reduction of over £1700 - like my own accountant says, if they can drop it that far then they've definitely overcharged in the first place... but hey! It's over and I can now relax and focus on the wedding - phew.
Thanks to all for your help - I really appreciate it.
Jo xxx