I need to do some rewiring in my kitchen. It has a concrete floor, and
the easiest way to route the twin & earth would in places be under the
floor. Once everything is done I'm intending to put Wickes electric
floor heating on top followed by ceramic tiles.

So, what I'd like to do is to put my SDS drill to good use to gun up
some channels in the floor, lay the cables and fill in the channels
with mortar.

Is it OK to do this? Must I use conduit (in which case I'd go for
http://www.screwfix.com/app/sfd/cat/...81966&id=12389 )?
Are there rules about the course the cables must take (no diagonals,
etc)?

While I'm at it I intend to put some cat5 and coaxial cables in as
well (although not to close to the electrics), anyone foresee any
problems with that idea? I'm a bit worried that the underfloor heating
might bugger it up.

Thanks for any ideas,

Martin