Combe Martin to Woolacombe would be a great walk but it’s about 14 miles. This would take you past Widmouth Bay, through Ilfracombe, through Lee Bay, around Bull Point and Morte Point and into Woolacombe. You could shorten this to 8ish miles by starting at Ilfracombe. Or you could just finish at Lee Bay.
Another option could be Valley of the Rocks to Combe Martin, about 12 miles. This is a tough one though, and includes in and out of Heddons Mouth and the highest point on the SWCP - Great Hangman (about 900ft I think).
Both great walks.