All your posts brought tears to my eyes. Thank you so much for all your kind words and support. At the moment, I feel I need it.
Mrs Kane ... I'd be more than happy to take up your kind offer - Feliway/Pet Remedy/Zyklene seem to do nothing for him. Just let me know costs of item and postage etc. Very kind of you to offer - I'm very grateful.
Julie My thoughts are with you ... hope your fears about Barney are unfounded. Keep us posted.
There's no doubt that Blackie is a 'difficult cat' ... the big improvement in him from being 10 years with my mother is that he is friendlier to house visitors, once he's seen them a few times. He took zero notice of us when we used to visit/stay with Mum and to be honest, he was such a 'tetchy' cat, we didn't like him at all. The change in that side of his temperament was astonishing once we took him back to our home in Kent - though the 'tetchy' side does raise its head now and then!
So to the vets we went this morning - and having known Blackie all his life, she takes my worries all in her stride.
As far as the bald spot on his forehead, she checked him again for fleas and ear mites - none. She listened as I explained about him going in/out of his tray. She thought the belly licking and bald spot could be due to a problem he was having with his bladder but as he'd urinated a normal amount in his tray this morning, this may well have passed. The different changes in his environment probably had upset him, causing him to lick his belly more and given rise to the bald spot on his forehead. She said that once Blackie realised 'life was back to normal', that nobody was going to leave the house and he wasn't going anywhere else to stay, he would calm down - but warned it might take a few weeks.
I thought she may have given some steroid ointment to put on the bald patch but she suggested I try Vaseline to keep it moist. I know she's a vet that doesn't like to hand out steroid treatment like confetti.
Now to the other problem which has been playing on my mind since March when Blackie had a broken upper canine removed causing the lower one to rub against his upper gum and make it sore. At times I've seen him not closing his mouth properly to stop this irritation. She suggested this was just as likely to be causing Blackie stress. She thinks the lower canine could be filed down slightly but this ought to be done by a vet who specialises in veterinary dental work and is going to give us the name/tel number of a clinic where we can take him to be assessed. Not something I really wanted to be done unless necessary, but if it makes Blackie feel more comfortable, then it will be done.
As far as his early stage CKD is concerned - absolutely fine for me to go on feeding him his beloved Felix (

) and add a small amount of Ipakitine to each meal - making up to 2 spoonfuls per day. There will come a time when he has to go on specialised renal food and a phosphate binder but that time hasn't arrived yet. Next urine test in September.
Lastly, his weight. It had gone up slightly - 0.2kg to 5.7kg and she told me to cut his food down slightly to get it back to 5.5kg.
Sorry for long post - had to get it all off my chest
Thank you all again for the support - it really does help.