I'd go direct, pretty much, routing through the SE corner of Boscombe MATZ (or above it), north of Compton Abbas, south of Yeovilton, overhead Exeter, slight dogleg to pass south of Princetown (and the Danger area). I'd RIS from Boscombe, who will had you off to Yeovilton, who will suggest you contact Exeter, who will suggest you contact Plymouth Mil who may had you to St Mawgan........(all RIS).
Very easy and nice route, have a nice flight!
