You sound like you've really gone into this, so assume you got independent valuations from estate agents. My heart goes out to you. Part of me (the stubborn side that sometimes cuts my nose off to spite my face) feels I would sit there like a pain in the backside ruining his development plans until he ups his price. But of course, it's a standoff situ if you do that and he may just go right ahead with you in the middle of the dust and then being overlooked. Do you feel the valuation is much lower (prices have increased past year) than you would've expected if you had decided to sell prior to this? You could say you want more, or you're going to your MP, Watchdog, Angela Rippon! you know the sort of thing. See if you can squeeze any more (be a pest, keep ringing him up). The sensible side of me, does think living there through the building works, then being overlooked by flats will spoil your forever home. So unless it's a completely unreasonable offer, perhaps go through the upheaval. Did you check whether your neighbours got good prices? Although he is arrogantly telling you, being last, your house isn't not worth what it was due to 'his'! development plans, at the same time, he won't want you sitting in the middle moaning about the dust and noise.