It turned out that my black OMD . . . (which I slammed onto a rock in Crete with all my weight slipping down some scree) had a problem working with the grip (sometimes it did, sometimes it didn't). It worked perfectly for the rest of my holiday - this was a major fall, and something of a miracle that the camera survived at all. . . . anyway, this was hardly a warranty issue!
So I sent it to Luton camera repair services
They completely replaced (the rather scratched but otherwise okay) base plate and battery door - they also fitted a new eypiece cup (mine was lost) and checked, calibrated the camera and updated the firmware.
The camera came back today looking almost like new - and working perfectly. It arrived in a rather nice Olympus tin.
The price was £140 for the whole thing (including postage etc.). They answer the phone, they answer emails, and they are accredited warranty repairers as well.
I'm very pleased, and very impressed . . ..