Hi HeliAv8tor
MBJ was nearly right but Thurston's is now called London Helicopter Centre after a relaunch in October of last year.
If you are serious about a conversion on a As350 and wish to discuss it with Peter Abbott, be quick as two of them may be sold in the next couple of months. They do have a number of Jetrangers however, you may wish to try the Colibri EC120 they have there, it's great to fly.
I cannot give you any guidence on price but I think MBJ was on the button.
All the best