Now that I got you to go with the plaster ceiling, I'll tell you that our floor is wood (solid oak). It is tough, good looking, and warm to walk on (and to look at!). However wood does scratch and mark, no matter how careful you are, so unless you are willing to accept that as part of its "character ageing", it may not be for you. However if you go for tiles, choose the colour and texture carefully, and tray and give the space some visual as well as physical warmth. The advice re under tile heating sounds good, cos remember this room will probably be used in winter too, so it should also be warm and well insulated.