Centralising the distribution point is a good idea, however you don't necessarily need the boxes to be located at that point.
I would consider doing the following:
Run 2 Coax cables to each room, terminating into 'F' connector faceplates, have the cables from each room run back to the cupboard. Select 2 rooms to be main rooms and run or 2 additional coaxs with faceplates. (c13846 on this page
http://www.satcure.co.uk/accs/page15b.htm - you will need standard single (2) or double (4) gang patress boxes and C12846 (2) or C12843 (4) module face plates)
Using the houses around you, get a rough idea of where you can put your sky dish when the install is completed and run 4 coax cables from the cupboard to around where you wish to put the dish, leave plenty of slack!
In the cupboard, install a F connector patch panel (basically 20 'F' barrels mounted on a plate with fixings for rack install or onto some form of frame), terminate all the cables run from the rooms into these panels, terminate the dish feed cables into the panel. (Here
http://www.canford.co.uk/commerce/item_48-4041_2006317.aspx)
Make small patch leads and connect the dish feed ports to the room ports where you want the sky boxes to be installed.
Connect a RF signal booser / repeater (with DC pass-throu) outputs to the other rooms you wish to pipe the sky into. I would recommend a booster for each zone, as using different RF channels can get messy. I would recommend one with F connectors on (like this
http://www.satcure.co.uk/accs/page15.htm the SLX4CF)
Connect the RF2 outputs from the sky boxes to your spare 3rd coax in the main rooms. Turn on the RF2 power in the setup menus. Make sure all the red lights on each remote eye come on! You will want an F to RF cable, or a converter (easily availible from Maplin or similar)
Get hold of some magic eyes which are connected via an F connector (get them here - the VisionLink range
http://www.satcure.co.uk/accs/page3.htm
Connect the magic eyes to the wall sockets using standard F patch cables.
Connect the sky boxes in each room to the TVs there.
Purchase a 4 port LNB for installation onto you sky dish if you choose to have sky installed from 'Sky'. If you get an independant, request a 4 port LNB for your dish.
When its install time, request that they connect all 4 of the supplied cables to your 4 port LNB. If you have patched it right, your dish feeds should get to the boxes in each room with the returns being piped around whereever you select.
This assumes the following:
You have a budget of up to £200 for parts and cable (depending on length, can be around £25 per 100m).
You know how to terminate coax with F connectors (either twist on or crimp on (crimp tool required!). There are guides on the sat cure site above if you are unsure.
You are happy mounting the faceplates into the wall (terminating into the faceplates is simple stuff!)
I have recommended running cables in pairs becuase when running 1, you might need 2 later on. As Sky+ or HD need 2, having 2 in each room means that sky boxes can be moved around to most rooms without the need to re-cable. Also, if you ever wanted to go to Sky+, you should always have enough ports for this, similar theory for the dish feeds, although you may only need 2, you got 2 spare for later (another multiroom box, or a sky+ box)
Hope this has made sense, I have implemented very similar myself (hence all the links where I got my stuff from!) so any questions I will be happy to answer.