[Halcyon]

Going the Wireless route is your best bet to avoid you having to put down cables all over the place, which may be against the house owners terms and conditions.

I'd say get everyone to chip in and get a wireless card in each of their PC's.
Who knows, may be some already have a wireless card in them already, eg. laptops with centrino mobile technology. Check to see.
PCI wireless cards are cheap too now so should'nt cost much.

Then you need a cable Wireless router. Make sure that it is not an ADSL router as that would not work on the NTL network.

Check out anything by Linksys, I've always found them good.
It wil be quite easy to set up too, and you wont have wires all over the house.

EDIT: One of the main things I'd observe when having 5 computers on a 1mb connection would be to be careful how much you download. If all five of you are keen downloaders, then you may use up your monthly cap, and a bigger connection package would be needed. It all depends what you use the net for really.