Hi, after doing some research on this I found an excellent application called Twitter Friend Adder.
I've been using it for just under a week now and I've averaged just over 100 followers a day - 639 up to now in 6 days! It's very cleverly programmed so you don't get banned by Twitter.
It can get a little more complex what your using multiple twitter accounts but to get around this you can use proxies :)
You can find it here:
Go to this site and you are added to a list and get tonnes of followers, but you have to add a few as well