Especially when you live outside the UK... Here's what I did:

1. Got myself a vitual UK post address (aka mail forwarding). There's many UK based companies/individuals who do this for a fee. I used these guys here but I cannot yet recommend them as they have not forwarded any letters for me yet; all I can say for now is that email communication has been optimal and their fees were reasonable (60.00 GBP for 3 months service and 25.00 GBP pre-paid postage fees - they charge about 1.50 GBP for each forwarded letter from UK to Italy
2. Having a UK based correspondence address I was the able to use the Money Claim OnLine (MCOL) service of Her Majesty's Courts Service. It won't cost you more that 25 GBP to use it for a small claim of a few hunded GBP and you can add this cost to the claimed amount (you can even ask for interest).

Good Luck!