This website, startups.co.uk explains that money may be made on SMS (the SMS Gold Rush) but has some good advice on the legalities:
Some services that are legal in one country may be illegal in another and often the interpretation and implementation of regulations can be different in the same market. For example, Vodafone UK does not allow micro payment services for all of its customers and 02 only makes such services available to its contract customers due to individual interpretations of the recent E-Money legislation.
