Thanks but I've got off my lazy backside and found this service: http://www.cbfsms.com/ I'll test it out to make sure it's not a 'mobile number farm' harvesting mobile numbers to sell to spammers and if it's good I'll recommend it to all, if not, I won't
Update: If you use the free service you get advertising sent with your SMS message. If you sign up for £15.00 to the VIP service the advertising is not sent with your SMS message. According to the Terms and Conditions your mobile number and those who receive your message are protected and not sold to third parties etc. VIP cost per SMS = £0.05p. From what I can see you pay initially for upto 300 SMS messages and can receive replies only via your mobile. I would say unless you send huge amounts of SMS per day it is cheaper to go via your mobile network, but if used heavily the VIP service might be worth looking into