I’ve stackable Wilko (RIP) plastic boxes I use to store malt in. Some loose, some in sealed bags. I reckon I’d have enough storage for 25kg if I repurpose some FV’s for sealed grain.
Bathroom scales, personally I prefer the ones that say you’re lighter than you are, my in-laws scales are great for this, mine no so great.
Exact accuracy isn’t an issue, 25kg is heavy and a lot of beer, even if it’s a bit lighter or heavier.
I’d make use of any base malt really. I usually brew pales, weiss biers, saisons or stouts. So I’d be happy to go halves with you if you want.
I’m pretty local Sherwood NG5, so arranging meeting should be reasonably easy. (If you want to go ahead).