I know Clerkenwell Screws well, ride past them every day on way to/from work... Only been in there 2 or 3 times but not been disappointed yet...

Metric series Fine (as opposed to the more common 1.75mm Coarse) isn't that hard to find on eBay or other stockists online ... but be careful Fine can mean 1, 1.25 or 1.5mm pitch for an M12...