It's only been a few months since you posted this, but I'm curious to know if you've come across any additional or supporting information?
Another potential verification for the Keighly (Leeds) source of the family would be to get some male Stell there to contribute some saliva for a Y-DNA test.
One of John's living direct male descendants here has already done so (Ysearch.org user QWQKY).It's a 25-marker kit with results almost perfectly matching the Y haplogroup I1(Norse).[This would make sense considering the Viking incursions into that area starting about 886 A.D.]
Anyone know of the Stells still in the York or Leeds area?