I found a pretty good pattern. Check out this table:

Discussing this last night, someone conjectured that the name 'shallot' might come from a longer French word like 'shallotte'—which answers.com confirms: "Obsolete French eschalotte, from Old French eschaloigne, from Vulgar Latin *escalōnia. See scallion." The modern French is found to be 'échalote.' So, what at first seems a curious exception turns out to have roots.

The accent I'm calling "No. of England" is, in all likelihood, not that at all but some other, more mysterious cross-section of British society. I will attest that I've heard these pronunciations among several people, in meatspace and on telly, too.

Repudiations & criticisms are heartily encouraged.