After lots of to-ing and fro-ing the pistons on the passenger side caliper showed no signs of shifting 

With the memory of a rather unamusing Renault 5 crash in the back of my mind, I decided not to bother with cleaning up the old calipers and getting a service kit, so one call to the local factors and a few quid later I’ve got a pair of reconditioned ones. I had thought I’d have to start mucking about with sourcing a fitting kit (pad shims, clips, pins, etc) off of eBay, but got a nice surprise when I opened the box and found they were already included 

Replacement M16 front brake calipers for Capri

They’ll hopefully be going onto the car tomorrow, probably after I’ve been to the local Steam Fair & Vintage Rally