The basic pay-and-go offering is a great deal with 8p per min calls and 4p texts which compares favourable with other providers but add a 'goodybag' and things start to get a whole lot better. Once you have topped up you have the option to purchase a goodybag which is essentially a package deal. You can view the current deals to the right of this page.
It does seem a bit of a pain to have to top up and then choose a goodybag but you do get the option to queue up 2 at a time which is handy. Having come from being on pay-monthly for a while this seems a bit laborious as first but definitely worth it for such a superb deal.