NC because outing, but I can relay our experience as a buyer, which resulted in our being the winning bidder on a house from a field of seven bidders despite (according to the estate agent) our not having made the highest monetary offer.
The best advice I can give is this: try to speak directly with the sellers, and take that as an opportunity to find out what they want, and to build their confidence in you as buyers.
In our case, the estate agent had us that they wanted to sell quickly, but from speaking with the owners, we worked out that they wanted a relatively quick exchange in order to get financial certainty for themselves, but they also wanted more time before having to move out. The estate agent either hadn’t listened to them or wanted a fast completion in order to get their commission faster. Knowing what the owners wanted gave us a huge advantage over any other bidders who had only listened to the estate agent.
Since we were chain-free, we were able to offer them a «long stop completion» , and we ended up agreeing a completion date more than three months after the exchange. There was some risk for us to that, but we could afford to take it, and we trusted the sellers to take reasonable care of the house between exchange and completion, plus we were doing a complete refurb anyway so any cosmetic damages would have been a non-issue.
We did also write a letter, at the request of the estate agent, and we think that may also have helped us to win the house. But most importantly, we sought out the sellers when that was possible during a viewing, we listened to them, and then we gained their trust that we could and would stand behind our offer. With 1 in 3 house transactions falling through, that had real value to the sellers.
I have heard the poster who would have been put off by a letter, but I should think it would help with most sellers, provided it sticks to elements that support your capability and your motivation to follow through with your offer. We wrote about being chain-free buyers so not dependent on another house sale, with a large deposit so very low financing risk, able to offer huge flexibility around the timing of both exchange and completion, and being highly motivated to move to that specific area due to our children’s school locations. It worked!
After all of our various experiences with London estate agents, both on the lettings side and on the purchasing side, I have become ever more convinced that the best approach is to speak directly with the principals (either sellers or buyers) as a better way to get truth and transparency. The estate agents have so many other houses to deal with, and are likely to forget important details about what the sellers want, plus they are sometimes, er, economical with the truth ... Meanwhile, your written offer, with the details you choose to include in it, should get handed over without modification to the sellers.