What you need is some trunking burying in the wall. Trunking comes in a variety of size groups: micro, mini and maxi. The larger mini trunking and the smaller of the maxi trunking profiles are generally in the right sort of size profiles. Maybe have a look at 38mm x 25mm as a starting point. Bear in mind that you need to get the plug ends of AV interconnect leads pulled through the trunking, possibly when there's other cables in there too.
As for cables, my standing advice to all house owners doing a refurb'/extension project is don't let the builder or spark supply any aerial/satellite/CCTV/Ethernet or any AV wiring unless you pre-approve their product choice. With respect to the trades, 99 times out of 100 they'll go for the cheapest crap they can buy because they [take your pick of any/some/all of the following] (a) don't understand why the cheap stuff is crap, (b) don't care, (c) just ask their wholesaler for "some aerial cable". The chances are you're going to pay through the nose for whatever they supply anyway so you might as well get something decent. Having said that, cable isn't that expensive, and the difference between rubbish and the good stuff is often just a few tens of pence per metre. To put it another way, for every £1 you save buying the cheapest coax or Ethernet cable it will cost you £200 in fees for remedial work to rip it out and replace it with the decent stuff you should have bought the first time round. Do you really need that hassle?
For aerial/satellite and some CCTV applications then Webro WF100 is what you want to buy and install.
Ethernet: Install Cat 6a cable and avoid anything that is labelled as 'CCA' which stands for 'Copper Coated Aluminium'. What you want is solid copper for the conductors and not aluminium with a bit of anodised copper plating. Aluminium is far more prone to breaking and has higher electrical resistance.
For HDMI then choose High Speed-rated cables. Go for a product description that details 100% copper conductors and triple shielding. Gold plating on plug ends is common but serves little more than to add some bling factor.
Running the cables: My second bit of standing advice is don't let builders or sparks run your cable unless you have pre-approved their wiring plan. Mains sockets and lighting rings are wired daisy-chain fashion but AV and Ethernet cables rarely are. We in the AV trade generally wire from a single source device such as a sat' dis or CCTV cam' direct to its relevant sink device such as the satellite receiver or CCTV recorder.
Aerial/satellite and AV cables radiate and pick up interference, and that's partly why you want decent cables because they have better shielding to reduce both problems. One common issue in part/whole house structured wiring jobs is to avoid running signal cables parallel to mains cables where possible. Mains and signal cable in the same bit of trunking stands a fair chance of creating mains frequency interference
on picture. To reduce that risk then leave a 10" gap between such cables when running parallel. Put the mains cable in one trunking and the signal cables in another.
Covering the bases: I'd always recommend wiring for a TV aerial even if you plan to use Freesat (and probably streaming). I have seen on occasions where the satellite signal gets blocked in adverse weather conditions. This rarely ever occurs with Freeview so it's good to have a back-up. Every TV sold today has a Freeview tuner but not every TV can pick up Freesat. Who knows whether the next TV hanging on the wall will have a Freesat tuner?
Have a think about where you might want a TV recorder and wire signal cables to that point too. Since it is common to find Freesat and Freeview recorders with the ability to pause live TV and to record one channel while watching another then it's often the case that the recorder becomes the TV tuner and the TV on the wall plays dumb. Remember too, a Freeview recorder can run multiple tuners from a single aerial cable connection. A Freesat recorder can't do this. If you want to watch one channel while recording another then the recorder needs one satellite dish feed per tuner. Hence a Freesat TV along with a twin-tuner Freesat recorder will need 3 feeds from the LNB on the dish.
The future of TV is looking more likely to include a lot of streaming. It's possible to do streaming to the TV via WiFi, but ask yourself whether that will still be the case if there's more competition for that wireless signal. Streaming to one TV or maybe two at the same time might work okay; but what happens when streamed TV is also being watched by a tablet and a mobile phone while someone else in the house is trying to game online? Wired Ethernet connections don't suffer these issues.
