Thanks for the replies - I've ordered some from an Ebay seller that seem suspiciously cheap but should be good enough to get an idea of how useful these mics are going to be to me.
If all is good, I guess I'll try making my own - the sense of satisfation from doing it will hopefully outweigh the fear that they'll fall apart at any moment.
I dunno... I reckon UK electronics/audio places don't have quite the range of stock their US counterparts have.