Our house is 1974 vintage, and we bought it specifically to add a large side extension, and consequently the main router and networking gear sits one side of the original exterior wall, whilst this does have fairly good coverage there were some dead zones. The whole house has been renovated by me and has cat5e to pretty much all the rooms and the loft where I have installed a WAP1750 access point, between the main router and this I get pretty good coverage.
PS That Stramit board looks horrible, our original partition walls are 60mm thick, made of plasterboard with a cardboard reinforcement in between, not very strong and no good at blocking sound, but very easy to push a conduit down from the loft.