Places to try:
Qinetiq at Boscombe Down
AgustaWestland at Yeovil
BAeS at Warton
P&M Aviation at Manton
CAA at Gatwick
NFLC at Cranfield
FRA at Hurn
LAA at Turweston
In each case, I'd say, look them up, do some homework, contact the head of flight test directly/Chief FTE/Chief Engineer directly, and ask very nicely by letter or email.
And best of luck.
G