Moved fairly recently. A call to the Estate Agent is enough, they are bad for not getting proof and plenty will take your word for it when you don’t have funds which causes delays. So make it clear you do and have sold your house etc, also find out the state of your chain as this will all sway the buyer. We turned down a higher offer from a buyer that had not even accepted an offer on theirs. We were also asked to take off the market which in reality means Sold STC on Right Move etc and taking the sign down, no more viewings. Solicitors will ask for official mortgage docs and funds later down the line.
On the house we bought first offer was 15k below asking and went up every few days in smaller and smaller increments till they caved, took a while and ended up pretty close to the asking anyway, although they did state ‘Offers Over’ and were initially very put out we did not abide by that, lol the cheek. I’m sure the estate Agent would have let us know if any other offers had come up between times.
Also, call your Solicitor minimum once a week for an update because they all seem to prioritise based on harassment. And don’t panic when you get snotty letters from theirs about covenants and certificates, they are not deal breakers, the buyers are most likely not as obsessed with them and just as keen to get moved.