Well, it's relatively good news in that the result of this morning's blood test indicates that the problem is an excessively low level of calcium. This is despite my having given him a higher than usual dose of calcium/vitD tablets after his seizure yesterday. The answer for now is to supplement the normal number of tablets with extra vitD - we are getting hold of those soon. Meanwhile he seems happier today has started eating again.
I will update when we've seen how he progresses. By the way, his name is Bing (after Chandler!) and our bitch is Rosie, aged 7, because of her colour - red(ish!). We also have Poppy a 9 year-old Great Dane bitch, Pepsi, a blue Burmese cat (neutered queen), Zach, a 25 year-old Westphalian gelding (German warmblood) and Sassy, a 13 year-old Morgan mare and Buzzy (they both are - as named!), her 5 year-old gelded son!
Thank you all again. How do I upload pics on this forum please?