I wouldn't go too crazy asking dozens of breweries - you'll just end up making breweries think that homebrewers are just timewasters who cause them work without actually ordering anything, and it ruins it for everyone.
They all buy from a handful of the same suppliers so the prices won't be hugely different, almost certainly less than the cost of the petrol for going to Cheddleton (never mind the time factor). And to be honest, this kind of deal is not just about money - it's about building relationships, which you can benefit from by learning how the pros do things and also in a time when LHBS's are disappearing, a good relationship means that if your smackpack doesn't work or there's weevils in your Munich, the brewery may be able to help you out with some yeast or malt. And obviously they hope you'll buy some beer from them.
Given that homebrewing is hardly an "essential", I'd be embarrassed to be quibbling over pennies when these businesses that contrbute so much to the local scene, are struggling for their livelihoods. I don't think it's an exaggeration to say that 20-30% of breweries in Tier 2+ areas could be gone within a year -
Cheshire Brewhouse is already up for sale and it won't be the last.