Hi Jack
The decoy Q airfield for RAF Warmwell was at Knighton (Military GR 141/245074, NGR SY 812866) but the site is now covered by the defunct nuclear power station (being de-commissioned) and the Dorset Police HQ. Access to the latter area would be difficult, as could the chances of finding anything decoy-related.
I have researched the Dorset History Centre archives but they have nothing on the decoy (Oh, what a surprise! - their records are terrible!) and the only hard reference I have is in Colin Dobinson's tome 'Bombing Decoys of WW2'.
If you would like to visit, as I am at Bere Regis (not a million miles from Warmwell) and would love to participate in a 'ramble', but whereabouts in the world are you?
Best regards
Paul Doyle
(author & researcher, owner of Forward Airfield Research Publishing)