tiling bathroom floor - should I leave a 4mm space between shower tray and loo etc or can I tile flush to edge?

a small gap between the sanitary ware and tile is a good thing especially if the tiles are fixed to timber , this will allow for some movement in the floor and avoid cracking the tiles or the pan. Just make sure that the silicone bead will cover the gap that you left so you get a nice finish. sam

You can tile flush with all Sanitary Ware, but usually you would put Basin/Toilet on top of tiled floor. Bill Pipe Dreams Plumbing Services Bournemouth

there is no problem leavin the gap so long as its no bidder than 4mm, the gap will then be concealed with sealant so would be able to see it anyway. If you tiling onto a wooden floor the gap would be a must anyway!