Hmm, I'm not sure whether it is possible to describe Methodism as a 'block' to Unionism in quite that way, and it may be preferable to allow several parallel interpretations of events to co-exist.
The roots of Methodism in their political context are very well explored in
England in the Eighteenth Century by J H Plumb, 1964, Penguin Books. Chapter 3 is probably the priority read. Methodism had strong Tory and Anglican roots, seeing itself as a religion for the poor, rather than of the poor. Thrift, abstinence, hard work and concentration and ultimate salvation were the essential virtues, says Plumb, rather than the political radicalism of other Dissenting faiths. There is something in the midst of that rather basic approach that captured the miners, and whether, in later years, what was seen as a dilution of these core values led to a development of 'Primitive' Methodism, for example, would need further reading on my part to offer any opinion at all.
Plumb was regarded as a left-wing historian and his views remain of interest.
I think you are exploring a pretty rich vein here and it will be interesting to see what conclusions you draw.