10 meters is bloody long cable!!!!
Why does it need to be 8 way? or mean 8 gang maybe???
I know cables over 10 meters long get hot and I mean very hot and can become brittle. Unless you move to twin and earth 1.5mm+ depending on load and amperage.
Aren't extension leads 1.5mm anyway?
Unlikely you'll get 2.5mm as it's too large for a 13amp plug.
Depending on the load of your kit you might get away with one but two would be better.
Make your own?
Am not talking about the white stuff the grey twin and earth for electricians.
No its not the same.
As above, just make your own!
How many watts does all your equipment require if all in operation at once?