MYT is upstairs now. Currently round the back where SAS checkin. TCX are in their usual spot from desk 1 onwards. As of 1st March both TCX and MYT will checkin from desks 1 to 25, I think Swiss and a few others are going back behind MON/ZB checkin. As of 1st April, MYT/TCX will of course be one airline and will use most of the desks along that 1st bank, with just LH right at the end.
mmeteeside, I worked in T1 last Sunday morning and it was very busy at security up until around 6 and then quiet up until half 8 before it got busy again. I suggest you try and get through security between half 7 and 8, that should be the best time. Of course with it being half term, there will be extra charter flights so that could alter things slightly.
RE car park buses, all MAG car park buses (ie - Long Stay, Premier Park, Shuttle Park) pick up/drop off outside every terminal and have been doing for months now. Some private car parking companies may still be using the station but as far as I know, most are using the stops outside all 3 terminals.