That sounds like a traditional agreed value policy. Much less of them around now and they are much more picky on accepting cars on agreed value. Much harder to get agreed value on modified cars too. Although there are alternative schemes using "indeminified value" that use the proven (through receipts) valuie of the modifications.

If your car has shitloads of expensive mods, then an indemified policy may be better as long as they agree the value of the parts based on the receipts when you take the policy out. Where as a agreed valuation on a highly modified car will almost certainly NOT cover the value of what the mods actually cost.

eg my cossie puma would probably get an agreed value around the 10k mark at best these days. However the cost of the mods was 3 times that and is insured for the original cost. An agreed value policy wouldnt pay out enough to get anywhere near to another similar spec car, however and indemified value policy would.