For years now I've used the Bead and Jewellery Shop 95 Crown Road, St Margarets, East Twickenham, TW1 3EX. Open 10 am to 4 pm Tuesday to Saturday and there is parking around the corner in front of Marble House. They can re-string necklaces including pearls (more expensive if you want knots in between each pearl) and will also repair catches on brooches, replace missing stones in brooches, and put new findings on earrings. They generally send repairs and re-stringings away but they come back pretty quickly - within a week or so, from memory.
Marie Power ● 2016d