Is D&G undervaluing our old Hotpoint BFI620?

We have been paying Domestic & General a lot of money over the years for domestic appliance insurance (I wouldn’t now recommend doing this kind of appliance insurance to anybody). They have recently written off our Hotpoint BFI620 dishwasher, after one of the door hinges and spring broke. They are offering us replacements, some of which are “equivalent” and some are “enhanced” models. The four “equivalent” models are all Hotpoint/Indesit/Whirlpool. Judging by the current online prices of the “equivalent” models, they seem to be valuing our old dishwasher at around £300 (it’s “equivalent” value, not its value now as a broken and obsolete model of course). Also, when we look at the “enhanced” models, because these are supplied from third party sellers such as Currys, the value then placed on our old dishwasher is more like £240.

Our old BFI620 was bought in 2005 and we do not have the receipt for it, but do these valuations sound right to anyone? Feels to me like we are being seriously ripped off here. Anyone know what a Hotpoint BFI620 might have cost in 2005? Or how to argue for a better settlement with D&G?