Due to a change of plans and hemisphere for the month of June, I have an entry going for the Midsummer Munro half marathon at Box Hill on June 21 (so called because it includes 3000 feet of climb).
website:
www.trionium.com/mm
Looks like a great race, and entry is now full, so if you want to run let me know. It's easy to get to by train from London.