It just keeps on growing. The London Underground Wi-Fi network that is, with a further 20 stations now added to the list.Virgin Media has just announced the new additions, which are Belsize Park, Notting Hill Gate, Camden Town, Seven Sisters, Chalk Farm, South Kensington, Highgate, Swiss Cottage, Mornington Crescent, Bounds Green, Balham, Finsbury Park, Clapham Common, Holloway Road, Oval, Russell Square, Clapham South, Turnpike Lane, Lancaster Gate and Wood Green. More stations will be added early next year, taking the total to 120.If you want to use it now, just turn on your mobile device, find the network, then follow the sign-in instructions. Once in, you'll beer automatically connected each time you need it. At least, you will for now.As we enter February 20123, you'll need to pay unless you are part of Virgin Media's customer base or a network that's signed up to use the service. As we reported earlier, that is Orange, T-Mobile and Vodafone so far.If you are not on one of those networks, you'll have to pay. £15 per month, £5 for a week or £2 for a day are the charges, but how that will work in practice isn't yet clear. Look out for a further announcement as we enter the new year.But on the plus side, if you just want information and travel updates, those will be free for all indefinitely.