//...but it was the SNP back in 1979 who were her main backers.//
It's not that straightforward according to the article Corby kindly provided:
"Had the SNP not withheld its support, Callghan’s government might have staggered on – but only for a few months, as it would have been obliged to go to the country by October, when its five-year term of office lapsed. Either way, the SNP was not responsible for Labour losing the May election that followed the lost vote of confidence. Margaret Thatcher’s victory was basically due to the “winter of discontent”, an unprecedented wave of public sector strikes, which allowed the Conservative leader to credibly argue that the post-war settlement had to be overthrown for the good of the country. Perhaps the memory of that dreadful winter of strife might have faded by the autumn, and given Callaghan a better chance of re-election – but given the shadow it was to cast over the 1980s, it seems unlikely."
The memory of that dreadful winter would not have faded by the following autumn. Believe me, I lived through the 1970s and the memories have not faded now. Another five years like that (which would almost certainly have followed had Labour been re-elected) and the economic mire that this country had descended into would have been too deep to climb out of.
I despised the Labour politicians of the 1960s and 70s who allowed this country to descend into chaos and penury. They caused me and mine tremendous difficulties and inconvenience that took a decade to fully recover from. The difference is I've moved on, that was then, this is now, and I certainly didn't rejoice when James Callaghan died in 2005. It's a shame the "Thatcher haters" can't do likewise.