Source: the official IOMIB site, July 2006:

"Our station will be heard across the entire UK and Ireland as well as parts of mainland Europe on 279 kHz Long Wave and on cellular phones. The station will also be heard across much of Europe by satellite, around the world via the internet and on selected digital radio and TV networks."

In summary: Long Wave, satellite, internet, cable TV, and an unspecified method via 'cellular phones'.