A specialized engine test bed: The Folland Fo.108
http://en.wikipedia.org/wiki/Folland_Fo.108
http://www.aviastar.org/air/england/folland_43-37.php
http://www.historicaircraft.org/British-Aircraft/pages/Folland-Hercules.html
http://www.historicaircraft.org/British-Aircraft/pages/Folland-Hercules2.html
The Fairey Battle was also successfully used as a testbed.
With Bristol Taurus II: http://www.airwar.ru/image/idop/bww2/battle/battle-3.jpg
With Napier Sabre: http://www.airwar.ru/image/idop/bww2/battle/battle-6.jpg
With Rolls-Royce Exe: http://www.airwar.ru/image/idop/bww2/battle/battle-13.jpg
With Fairey P.24 Prince: http://www.airwar.ru/image/idop/bww2/battle/battle-15.jpg
With Bristol Hercules: http://www.thescale.info/news/publish/Fairey-Battle-Classic-Airframe.shtml
Experimental Canadian conversion with Wright Cyclone 9 as a safeguard against Merlin shortage: http://www.airwar.ru/image/idop/bww2/battle/battle-5.jpg
