I have to agree with ppilot. Technical interpretation of the regs allows you to log PIC time as long as all those criteria are met.

However, in your case, UKman, I'd say you could not even technically log that PIC time because you are only type rated AS AN SIC on your certificate. Also, as everyone else has pointed out, it would be counterproductive to log those times as PIC if you're looking to get on with another company someday (and who isn't??), since they only want PIC time counted when YOU are the final authority for the flight.