For connections, make sure the unit has a HDMI socket. All TV's marked as HD Ready (NOT HD Compatible) will have one. An HD ready TV will also have a horazontal resolution of at least 720 lines (as opposed to 480 on a standard PAL television)
LG and Samsung make their own panels, and both seem to be pretty reliable with good quality pictures.
For wall mounting, check that the TV has VESA mounting bracket holes on the reverse. This is pretty common now, and will allow you to use an appropriate VESA wall mount.
I remember from a previous thread that you had problems with a TV from Currys. You might wan't to try PC World (even though they are the same group) as they currently have Buy Now Pay Next Year on all large flat panel TV's.
As to plasma Vs LCD, there are loads of different opinions, and pro's and con's to both. Popular opinion seems to be coming down firmly on the side of LCD, but Plasma can represent better value.