The list price seems to be a very long way above anything that's been achieved for similar stuff in the area. List price is £400k, I'd generally . And by the way it's in relatively poor condition, e.g. many decades old/unexceptional quality kitchen & bathrooms etc.
I might say that recent transactions might value it at about £275k-£325k, maybe even £350k [it's unusual enough a place for more precision to be difficult]...
I was thinking about a £300k bid, would something like that [25% below list] be offensive?
Cash buyer, no chain.