The South West Coastal Path is 630 miles and includes Dorset, South Devon, Cornwall, North Devon and Somerset.
This route is 99 miles of the North Devon section of the SWCP (arguably the most beautiful). People have run the SWCP with Damian Hall’s record averaging 100km a day. Unlike the SWCP, there are no requirements to travel on any ferry so this therefore is purely down to the runner. In addition, this can be run in one attempt without the need to sleep. There is significant elevation gain. One end is Marshland Mouth and the other is Glenthorne beach.
SWCP: https://www.southwestcoastpath.org.uk/