£19.99 one off set-up cost

From The 3 Website:

No wires. No contract. Just buy a Top-up and convert it to the Add-on of your choice to get online almost anywhere with your 3 USB Modem.

Top-Up Details

Top-up costs vary depending on how much you buy at a time:

Top-up £10 and get 1GB for 30 days
Top-up £15 and get 3GB for 30 days
Top-up £35 and get 7GB for 30 days

Modem / Dongle

ZTE MF627 USB Modem
What's this?

Using Abroad

The standard rates for using mobile broadband abroad with 3 mobile are £3 per MB for selected countries, and £6 per MB for other countries.

Until 30th June they offer a 3 Like Home promotion, which allows you to use your service in selected countries for the same price as you do at home.

Click here for more info on using 3 mobile broadband abroad

Details, Compatability, Etc

FREE delivery available
Return Policy: Buy directly from 3Store online, and you can return it, so long as you return it within 14 days from the date of delivery.
Download Speeds: Up to 3.6 Mbps
Compatability: Plug’n’Playinstallation on Windows (2000, XP, Vista) and Mac (10.4 and 10.5)
MicroSD card slot, up to 4GB. (Card not included).