Last I knew it is illegal to carry anyone other than operating crew on the flight deck in UK airspace, this includes foreign carriers, unless there are no other seats available. i.e. if there are any spare pax or crew seats in the back it is illegal to carry jumpseaters on flight deck
Not so...several company Ops manuals in the UK have a little "get out" clause with words similar to....."at the commanders discretion"..or "flight Ops directors discretion"..etc
