If you are planning on having your dog micro-chipped it may cost you £30 but the Dogs Trust is doing it for free. I haven't looked into the 'small print' as I don't have a dog (yet).
http://www.dogstrust.org.uk/default.aspx
I have my fleabag felines chipped and it is reassuring to know that if they get lost they might find there way back home. That is
if Frankie survives the afternoon without me throttling him. ;-)