My two are both clipped off so at least they feel a little cooler. We take them out in the morning and usually around 3-4pm and just across the road from where we live is a river so when it's as hot as it has been recently both make a beeline for the water and go for a nice cool swim. As we both work from home I sometimes do take them out at lunch time aswell but we make sure we stay in the woods (again just across the road).
Holly likes to sit outside on her bean bag so i make sure it's in the shade (i put an umberella over her bed) and Henry likes to stay inside on his beanbag where it's cooler. We have wooden floors downstairs so when they are both too hot they lie on the wood and the other day I even found Henry asleep behind the tv where it is cool but i've never seen him do that before.
I fill their water bowls (one inside and one outside) with ice cubes in the water and put it in the shade, and I also give them ice cubes to munch on as often as i can. If I'm feeling soft I also give them a vanilla mini milk ice-lolly which they love (only 30 calories too).
I also make them special cocker ice-lollies. After our evening meal (hooman) if I've grilled some meat or fish I add water to the dirty pan and get up all the bits of meaty stuff, then I put it in the fridge and when it seperates the fat will float on the top; scoop the fat off then it's just plain meat juice. I then put it into little ice cube bags or little plastic containers and freeze. They love their meaty cocker ice lollies.
I also read somewhere that if the dogs are really hot then wet a hankie or tea towel in cold water and tie it around their necks.
Fingers crossed this sunshine lasts until our NW cocker walk on Sunday