Keeping to the seaside theme, Bournemouth would be good, Sandbanks also has a nice shared path along the beachfront. Can’t you just skate anywhere though? If you’re in or near London then any of the parks, Hyde park used to have (might still do) a biggish skate scene. I can’t remember the name of it now but there was a pub near Paddington where they’d all meet after skating and on certain weeknights half the customers would be on wheels.
When I was younger we used to skate all over the place. There’s a fella round by me that regularly skates on the road, I assume as a form of transport rather than specifically for exercise, he travels at a fair clip too.
Happy days, late night roller hockey in MFI car park, tin cans for goal posts, isn’t it? Marvellous.