pebbledash,
A tiler's job is to place tiles on walls or floor and finish same with grout. It is not to remove and replace any sanitary fittings [w.c, sinks, baths, showers etc] - this comes under a plumbers remit.
While it may seem a straight forward job to remove the sanitary ware it adds an unnecessary liability to the tiler [pipe leaks - you hold him liable - not covered under his insurance] and this is why I imagine none of them are willing to call you back.
You will find that many of the larger tiling contractors [linked with tile shops] will possess public liability insurance to cover any accidental damage by them however smaller contractors are less likely. This is no way reflects the quality of their work!
A good place to start is contact the shop where you bought your tiles and ask if they have a recommended list of local tilers [most do]. Once they are on this their work is in all likely hood of a high standard. If in doubt ask to see some of their work.
more often than not poor plumbing is the cause of leaks into other apartments - but on occasion poor tiling to a shower tray or bath is the problem.
Ó Murchú