Yes there are toilets all the way round the circle. At the start/finish at the Quay Climbing Centre, as well as on Exeter Quay (14 The Quay, Exeter EX2 4AP, over the bridge from the Piazza), in Heavitree Park (Heavitree Park, Heavitree, Exeter EX1 3DN), the Cake and Crumb Cafe in Marsh Barton (Alphin Brook Rd, Marsh Barton, EX2 8QF) and near Exwick Cemetery.