I buy mine off eBay . Progressive Life is good. I have just bought 3.6 kg and it works out at £5.96p a kg. The more you buy from them the cheaper it is. 7.2kgs works out at £4.37p a kg
same as pauline, good quality, good value and very quick delivery.
Charnwoods do 25kg for £58 but unless you have a lot of horses or can divide it up between other people, it will take so long to use it all that it will have started to deteriorate so better to buy smaller amounts and use it fresh IMHO.