In the case of Freeview, you will need to buy a Digital Terrestrial Television (DTT) decoder (also known as a set-top box or adapter), and you may also need to upgrade your rooftop aerial. DTT decoders can be had for as little as £30-40 (although there are more expensive models containing extra features – see DTT set-top box listing). An aerial upgrade will usually cost between £60 and £100. However, once you’ve spent these initial sums, that’s it: you won’t have to pay anything else to watch.

In the case of Top Up TV, you will need to buy a DTT decoder, as with Freeview, but you'll need to ensure it is compatible with the service (click here for a list of compatible boxes). Then you'll need to pay a £20 connection fee (£10 if you subscribe online), and an extra fee of £7.99 a month.

In the case of Sky Digital, the satellite decoder and dish are ‘free’, but you generally have to commit to a monthly subscription (from £13.50 to £40 a month depending on the package), and – depending on whether there are special promotions being offered at the time you buy – have to pay for the dish installation, too. This can range from £50 to £100. It is also possible to watch Sky Digital using a PVR device called Sky+, but this is a much more expensive option.

In the case of NTL and Telewest, no new rooftop installations are required. Instead, a cable is laid from the road outside your house to your TV set, and a digital cable set-top box is installed. Installation is generally around the £50 mark (but, again, it depends on what promotions are on at the time you buy), with subscription packages beginning at £15-£20 a month rising to around £40-£50 a month (these prices include a ‘bundled’ phone-line).