Plumbing: laying CH pipes in concrete

hi there

I'm looking at a job in Corfu installing an oil-fired central heating system over a concrete "slab". There seems to be several possibilities for the radiator pipework having chased suitable channels into the slab. Either:

1) Lay plastic covered copper (eg Kuterflex white coat double [outlet and return together] and screed over the top or,

2) Lay plastic covered copper (eg Kuterflex white coat double [outlet and return together] in a conduit to allow a certain amount of movement when the pipe warms up and screed over the conduit or,

3) Lay conventional copper pipe and screed over or

4) Lay conventional copper pipe in an insulting and protective conduit and screed over.

I am new to plumbing and do not know whether a screeding conduit exists for 2 and 4. Does anyone know if it does?

I am wary about (1) given the warnings about kuterflex moving when warm and stretching fittings out.

(2) seems better but is it a bit OTT?

(3) seems cheap but will the pipes also expand and what about chemicals in the screed eating the copper?

(4) seems ok????

Also what size pipe should I use? 10, 15 or 22? 15 seems a fairly safe bet.

Are the latest oil-fired condensing boilers reccommended?

Cheers Ange