Thank you once again to everyone who has offered suggestions for my elderly dog - to help him cope in this heat.
He is still panting if he is indoors (with windows and door open) but it stops when I put him on a towel over ice cubes, or a towel that has just come out of the freezer (thank you for that suggestion Rainbunny ). He is now barking when he sees 'his' blue towels, and runs on the decking to show me where he wants it.
Thanks also to Dawndonnaagain I have discovered that the dog doesn't mind a 'mist spray' of cool water on his back. He was abused and controlled with a water hose-pipe before he came to me, so he won't go in water and it took me 2 years to get him to accept bath-time without him thinking he was being punished. He may be old, but he has figured out that his mist-spray is kept in the fridge and he stands looking at the door to signal to me that he needs to be 'misted' again.
minesapintofwine I don't clip this dog - he is a short-haired BC, but the double coat is a problem in this heat. I know they are not supposed to be furminated too often (about once a week) but the heat is making the double-coated dogs shed far more. I am having to hoover my lounge twice a day to deal with the hair shedding.
MrsRossPoldark I did try the wet t-shirt, but his arthritis suddenly improved and he bounced away up the decking 
I think the look on his face said, "I may be old but I still have my dignity and I am not wearing a girl's t-shirt" 
HagOtheNorth My dog won't go near water because of water abuse before I adopted him. When I take him to the beach, he thinks that the little ripples of waves are coming to get him on his ankles! Having said that, he has swum in the sea twice! (1) To round up 3 boys who were visiting from Germany and staying with us. The boys didn't understand the ledges we have on NW coast and they over-stepped. He swam out and did the Border Collie 'round up' whilst he got the boys back onto the beach. (2) I took my brother to the sea for one last time before he died. My dog swam after him when he started to struggle.
(I am a proficient life-guard and was watching both times but my dog didn't wait to see if anyone else was going to the rescue - he faced his terror to save his humans.)
littlefrenchonion He is only walked in early morning (6am) and late evening (7pm) in this weather. He is allowed to sit on the shaded decking during the day - but no walks. He would collapse with the heat. He doesn't have fur on his belly because he is a short-haired BC. But furminating was the way to go the other night.
He already had one fan blowing on his big dog bed - now I've put 2 more throughout the home.
For those who have dogs with double and triple coats, this is the furminator demo video:
I brush my dog every day - but every week he is furminated.
THANK YOU TO EVERYONE WHO HAS SUGGESTED HELP FOR MY DOG. I did feel alone and quite useless when I posted. I know I have to lose him one day fairly soon, but I always want to do the very best for him because I have been privileged to have him in my life since he was 6 years old, and to get him to 16 years old is such an honour - and a testamant to the friendship we have had for the last 10 years.