, Guy, to APF, firstly.
Hopefully, with the word being out there, he (or his physical studio address) can be tracked down and made public. Reading these horror stories about this guy is mind numbing. He's had your poster a YEAR --you paid a deposit up front, and the he pulls this kind of nonsense?
And what gave him the right to carry yours (and everyone else's) posters off to Kent, in the first place? He should have contacted anyone whose posters he has and allowed them to come and get them, (if they so chose), or said it was OK for him to take them with him, before he just picked up and shifted that much further away, with all those posters in tow.
It all sounds like something the police could easily be brought into-- even to just help get the posters back.
Or Simes, since you always had a good poster outcome with Alain, do you maybe know or have his new address in Kent? If so, these folks
really could use some info or help, as Alain appears to have fallen silent with almost any client who tries to reach him, either by phone or email.