Thanks both - I think I was taking too literal an interpretation of the fact that LKH were listed as DAAIS providers, and obviously should have asked someone else. Didn't want to go higher than 3200 as I didn't want to go into IMC (see below)...
I'm a bit concerned if both LARS units would have been too busy, though, as I made most of the journey to Old Buck. IFR in IMC - only going visual as I passed overhead Cranfield. As it was I got a radar service from Brize until QSYing to Cranfield, so was OK, but would have been hoping for a radar service from Wattisham or Coltishall after that... Do LARS units prioritize aircraft in IMC outside CAS?
Tim