I hope I can help.
Mr NVN took a watch in to Asquiths on Northcote Road to have it repaired and he was very impressed with the price (they were about 50% of the West End equivalent) and the turn around (they took a week to fix the watch, he'd been quoted 10 weeks in town).
Anyway, while he was there he asked about your valuation question and they said it is very hard for them to do home visits. They need to use quite a bit of equipment and it's simply not possible to take it to everyone's house.
However what he did go on to say was that they usually set up a valuation account in these circumstances. You then bring in a piece of jewellery at a time and they will value that and add it to the account. Over a period you bring in all your jewllery and you get the full valuation.
The chap was very helpful, his name is Nic Coles, email address is firstname.lastname@example.org
tel. 0207 223 6473.
Hope this helps
ps full disclosure: they advertise with NVN but Asquiths didn't know it was Mr NVN visiting their shop. He didn't tell them and he paid full market rate for the watch repair.