click here explains how to set up an "Ad Hoc" network using two USB wireless adapters. Typically these will cost you £20-£25 each dependant on the speeds of 54 Mbs or 108 Mbs.
Assuming your NTL connection is Cable click here This will allow your machine to connect via cable (supplied) to one of the 4 ports and directly to the NTL modem. Buying one USB wireless adapter should allow the e to connect. The beauty of this set up is that your machine doesn`t need to be on for the other one to connect to the internet.
So Option one will cost £40-£50 and second option about £65-£70. Second option is by far the better option and offers better security IMHO.