You do know the SNP are known as the 'Tartan Tories' around the country? Many people still hold a grudge against them for their actions in 1979 which led to 11 years of thatcherism and the destruction of public services under her regime! Without them we may well have been spared that.
Many people during the lat election were scared that if Labour had a chance of winning the only way they'd be able to do that would be with a coalition with the SNP, something people in England and Wales did not want, and I don't blame them