John Stumbles wrote:

Unless you're just slapping down some cheap tiles to tart up and sell the
place I'd really, *really* rip up the chipboard and put down at least WBP
ply to tile onto. Water *will* get past your tiles (or more to the point,
grout) and the chipboard *will* swell up and probably bugger up the tiling.

Granted tiling directly onto chipboard doesn't sound too clever, but
could one not apply a suitable membrane (either just waterproof, or
something clever like Ditra) or boards (Marmox etc)?

Pete