Some good advice there.........
Your mobile phone, as long as it is 3G and you are with a mainstream network, will work but the connection/data costs will cost you a fortune. I would take a small netbook with you so you can connect to the internet and use Skype. Most higher class hotels will not charge you for internet connection. If you forget any leads you can soon pick them up at the 100 Yen shop (similar to Poundland). Tokyo is a fantastic place, if very different to the UK. The train stations are vast. Get yourself a Pasmo or Suica card and load it with cash and it will help you get about on the underground or JR Railway Lines. Please PM me if I can be of further help