Beware that if you go for a cheaper make it might not have been though the same testing as the Baileys and other well known companies put their feeds through. As a result feed can be contaminated. Another problem is that the way the feed is cooked will alter the different vitamins and minerals in the feed. So whilst you may be paying less you will be losing out as your horse won't be getting such good quality feed.
Ring the help line, explain the problem. It might be that Baileys have a cheaper alternative that will suit your horse.
Dodson & Horrell Build Up is REALLY good. It is more expensive than Baileys but I found I used less of the D&H than I did the Baileys one. It also didn't send my horse loopy loo!
I understand concerns about using local feeds, however, one must consider that the like's of Baileys are a far bigger company and although they may well spend more on research and testing, it is possible that they also make more per bag? All packaged horse feeds (along with others) should list ingredients in order to comply with EU legislation, so if you dont want to buy a cheaper one, check the ingredients of a bag you like and get some friends to chip in and buy the individual products and make a mix yourself - that way you know exactly whats in it!!!
Failing that do what we do, buy a locally made conditioing mix and add a bit of soya oil, garlic and any other bits your horse needs, oh and cherry chaff to stop them eating their portion quite so quickly! Works for me, even our 19 year old TBx mare performs well on it, and ooooh what a glossy coat (well when the winter shag-pile has finally rubbed off!)