We both agree and I wasn't challenging your understanding btw. I was just trying to expand on your point, you sounded anti dday renegotiation, that from a moral (right word?) view point it's fine to not like it but logically the proof is in the pudding. If the seller accepts the price drop then it speaks to the property now being worth that or else they'd pull.
The risk of negative equity is real over the shorter term but if you're moving somewhere for the foreseeable £10,000-£50,000 here or there isn't going to matter much. Just take the price and get on with the move imo. I personally wouldnt try renegotiate and risk chains falling through unless I'd overpaid by a decent amount or I had other options as leverage.