I was in Portobello Road yesterday and noticed that one of the screws holding my glasses together was working loose. So I went into the Poundland store there hoping they might have spectacle repair kits or a set of jeweller's screwdrivers - they sell a fairly good range of tools. Couldn't find either of them, but eventually did find a rather nice alternative - a miniature ratchet screwdriver with interchangeable bits. For a pound you get the handle and six bits - Philips 0 and 1, Pozidrive 0 and 1, and 1.5mm and 2.5mm flat blades, the smaller one just about the right size for glasses.
This isn't by any means a complete replacement for the usual miniature screwdrivers set, but it works and it's a good complement to a full-sized ratchet driver.