• Can I lay tiles over an existing floor?

It really doesn't matter which material you decide to use, whatever you choose I wouldn't recommend laying new on top of old, although it's tempting because it'd certainly save you some hard work but preparing the surface properly needs special treatment and the stuff needed doesn't come cheap either.

For a partiall tiling very often you'll find the floor isn't all the same level, so you'll probably have to trim the doors and depending on how you do it, possibly the doorframes too, which is quite a difficult job.

There are some special floors that help overcome this matter, but the ones I know of are all wooden floors, here we call them floating floors.

By hiring the right tools (a hammer action drill with a special chisel bit, ask the supplier), the job of pulling off the old tiles is much easier but a hard job nevertheless.

But believe me it's worth the effort.