My sister and her husband did this when they were buying their house in London and I am tempted to try. Essentially we are in a bidding war; neck and neck with another party; we are both in equally good purchasing positions. We desperately want the house, and can afford to keep bidding, but the price is getting to the point where the house will no longer be good value (it needs work). The asking price has been well exceeded at this stage.
We feel that a note might make a difference to the vendor's decision because DH and I are essentially good people, from the area originally but have moved our family around annually internationally for years in order to train in our respective fields (in our work we both help people a LOT- don't want to say what we do as it's totally outing), and would love to give our two girls the chance to settle in a lovely house, down the road from their cousins and grandparents, before our eldest starts school in September.
Would that info in any way swing your decision if you were the vendor? Or is it borderline psychotic / unethical? 