just a thought .... before you shoot anyone .... are you certain that the sockets are phone and not cat5/6 rj45 sockets
they do look quite similar to people
http://www.maplin.co.uk/searchtemplate.asp?cri teria=RJ45%20WALL%20SOCKETS
not the best pikkies .... but that's the point.
if they have done what you asked and installed structured wiring you can fit adapters so you can connect a PC or phone to the same socket
to do all this you should/must have is a patch panel used to connect the router or a switch to the sockets
http://www.blackbox.co.uk/ukhome.asp?cs=dvh&id =2&tx=Technology%20Overviews&bc=techoverviews/ installingscs
if you go for wireless
DO go for "N" bt have now made the change (their black range) - the rest will follow - the delay now is just a "cooling" period required by IEEE to be certain
N has far better range penetration - (I assume renovated refers to an old house - with thick walls?)
however - another option is homeplug
http://www.broadbandbuyer.co.uk/Shop/MFR/Categ ory.asp?CategoryID=255&SupplierID=1
but the best option is to get them back