Please see the 2 attached photos. The 1st shows the edge of the tiles, with the door closed. The 2nd shows the carpet edge metal strip lipping over the edge of the tiles (also with the door closed). The UFH doesn't go near the edge. It's about 6 inches away, so should be OK. The builder says he's going to borrow a specialist power tool that will let him trim the porcelain tiles up to the door frame, so the edge is in line with the door. The tiles should have finished under the door, of course, but at least if the edge is straightened, the carpet edge metal strip will be straight, and it won't look so bad. I know I could tell the builder he has to take it all up and re-lay it, including the UFH, at his own expense, but I haven't the heart to do it!