Is it possible to buy decent solder in the UK these days? The lead-free stuff that's sold now doesn't seem to work that well.

I was talking to an electronics engineer a few months ago. He worked for many years in industry with automated soldering equipment. Now he owns a HiFi shop, and runs the repair department.
He said that the biggest cause of failure in home electronic equipment now is bad solder joints, rather than component failure. He puts this down to the use of lead-free solder. The solder crystalises and fractures.

Fortunately I've got a large reel of proper tin/lead multicore solder, bought from RS Components when lead was legal.