I negotiated via live chat. I was hunting for discount codes. I wanted a 15% off on top of Dell's discounts and TCB was, at the time, offering 14%, but then it stopped. TCB/Quidco is never guaranteed, especially if you're using codes, so I just chanced it with Dell direct.
Mentioned I had a non-functioning work code for 10% and that ordering direct would mean I'd lose out on TCB/Quidco, so they'd have to lower their price more (they initially offered £1100inc vat and 5yr warranty).
I went back and we settled on £950. I was happy with this as I didn't have to run the gauntlet with cashback.
Sorry if above is against forum rules due to Dell being a competitor. Please delete if necessary.