Vodafone Data Network (Previously known as Merrac Ltd, then Paknet Ltd)
Paknet was started as a joint venture between Racal Vodata and Mercury, but is now owned solely by the Vodafone Group. It runs a standard X.25 packet-switched network at 8kbit/s radio link and provides seamless interconnection to any other public packet network. It has been used mainly for fixed applications such as point of sale (POS), telemetry and security systems.
Can I find any current links? Probably! I tried to include some here, but Vodafone seem to like breaking links every so often. So try Googling for Paknet.
... and here's a SMS Paknet FAQ.