You will get the imported malts in a 55 Lb sack = 25 kgs.
Maris Otter is the variety. It is owned now by Warminster maltings, which has the seed stock. It is grown across the UK by farmers, who then sell it to various malsters. Lets see - Crisp, Muntons, Simpsons, Baird, Fawcett, Glen Eagles and the mentioned Warminster.
The haze has to do with the growing season the last few years resulting in more nitrogen in the malt, which causes haze. Most of what we buy today is a blend of maybe 70% MO and 30% other varieties that have lower nitrogen, which gets the nitrogen value down where it does not cause haze. This caused a big discussion in our club, as it was noticed we are now getting a blend, not straight MO.
Find a malt you like for the money and stick with that until you want to experiment. Look at the Lovibond of the malt, in general you will get more flavor (toasty and bready) if the malt has a higher rating. For example Weyermann makes Pilsner, Pale, Vienna, and Munich from light to dark. MO malt can be from around 3 to 4.5, and there is even a Low Color MO that is about 2. The 4.5 is tosty-malty, the 2 is sweet malty-low toast.
Hope this helps.