We found giving the estate agents deadlines, on which date(s) we threatened we would definitely pull out, tended to get things moving. They are far more frightened of things going belly up as they lose their commission, whereas the solicitor will still get their money, or a proportion of it, whatever happens.
We also found it was mostly solicitors delaying things. Ours made a fuss about getting copies of planning permission/building regs for a kitchen "extension" that was actually an internal knock through into an old outdoor toilet/coal hole, years old, and a garage that predated our sellers, who had been here 7 years. I checked the current planning law myself and discovered that, even if there was no planning permission, the Council could do nothing as these were old works. However, on receiving the pre-registration documents last week from the sellers'solicitors, we discovered planning permission, 30 years old, for the garage and plans for the kitchen from 1979, all of which had been available all along if anyone had cared to look for them! But no, why would they do that? Far better to write to each other (by post, of course, not email) and suggest contacting the Council to see if these permissions existed!!!
No wonder they charge so much. They spend far too much of their expensive time wasting it!!