I was thinking of having the following wiring done by an electrician rather than having to call out multiple companies:
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Would I need to call out specialist companies for running any of those wires? The reason behind my thinking is that floorboards would be up so I could get all the wires run that I need and then call out specialist companies to attach their electronics to the wires.
A
good electrician could run all of those - in particular if they aren't being required to connect them up then it's no different that running other types of cable. However there are some caveats I'd add to that. I work in IT and part of my job involves installing networks - on some jobs we let the electricians who are doing the other work pull in the network cables and I'll terminate them later (saves two lots of containment or having to open up the trunking etc). Needless to say some of the electricians I'm happy to work with - others come under the category of "let them do it and find someone else to do your networking"
* New fuse board
* New electrical sockets (4 x double-sockets per room)
* New wiring for lights
* New light switches
* Power and lighting in loft
* Power and lighting in garage
* Security lighting
* Smoke and CO2 sensors
* External power sockets
That's all pretty much routine stuff, and in any case some of it comes under Part P and would have to be done by an electrician who is able to sign it off (or you'd have to go through building control which is likely to cost more).
* TV distribution system (running cables only)
* Alarm system (running wires only)
* Cat-6 (cables only)
* Phone extensions (cables only)
Fairly easy stuff, just a matter of pulling the cables in - some caveats come into play though. All of those should be segregated from mains cabling for safety and/or performance and/or legality. Ideally you need to keep them 4" minimum from any mains cabling, though that isn't always practical. On safety & regulatory grounds, it's permissible to have phone cables closer if they are separated by a solid insulating or earthed metal barrier (eg trunking or conduit). In commercial installations it's quite normal to use segregated trunking (such as dado trunking) where mains and data/phone run in separate compartments of a 2 or 3 compartment trunking.
One problem I see regularly is electricians who really should have a clue how to treat cable - but don't. Data cable and TV coax is especially sensitive to tight bends and kinks - in short they should never be kinked or bent tightly (I think 5xdiameter is considered minimum bend radius). A particular problem is the tendency for the cable to coil itself up into a rats nest if you run some off the drum/out of the box - so that when someone pulls it through into the next room (out of sight of the rats nest), they pick up a loop and pull a good tight knot or kink. Another problem is pulling the cable over sharp edges etc and damaging it - put that's a problem with power cable as well.
Your coax should be good quality copper foil screened cable rated for satellite use as that gives you the flexibility to use it for terrestrial or satellite. Cheap cable won't work for satellite, and is also more likely to pick up noise and result in 'hiccups' on the TV when (for example) the fridge switches on.
Anyone is legally allowed to connect your phone extension wiring as long as it's only connected to the line by plug and socket (which is built into the standard master socket used by OpenReach).
The last caveat is to ensure that you agree with all concerned what's happening before you start. It would be somewhat annoying to get all the cabling in, floors down etc, only for the alarm installer to either a) tell you something's wrong and he won't use the cabling you've put in, or b) there isn't the right type/quantity of cables and something else has to be added.
* Extractor fan in bathroom
I presume you mean the ducting for the fan ? I believe anyone can install that (assuming they know how to do it without b***ering it up.
As a more general question, how do you intend arranging your TV etc ? I'm a big fan of running cabling back to a central place so it's easy to switch things about as required. Many builders will still do what they consider a "standard" job and run one cable down to the main TV point, and then some others out from there to bedrooms etc. That's fine if all you want in the bedrooms is a feed off the back of your Sky box (or whatever). If you then decide you want satellite in a bedroom (whether Sky or Freesat) then you'd end up needing new cables from the dish to the bedroom. If you run a cable (or better still two) from each room to the attic, then you can feed them off a Loftbox if you want to feed your Sky box round the house - or extend them out to the dish if you want an independent satellite feed (or even use a multiswitch if there's a lot of receivers to feed).
You'll need to do such a "star wiring" setup for your network cables anyway - make sure you have network provision anywhere you are likely to need it, and don't forget that much AV equipment is now networked and you may well want a network point behind each TV.
