Dave

Hi julia......2/3 mm on walls is mostly used......and as you say 4/5mm on floors unless rectified tiles are being used then 2/3mm for floors are used as well.....just depends upon which tile is being used..sometimes joints of about 10mm are used on the likes of slate or quarries etc......

If you take a look around the tile gallery or users profile albums you will see loads of pics of various tiling projects differing in tile choices......