If Scotland had left the union prior to 2019, the Johnson majority would have risen from 80 to 110
In 2010, there's no coalition with LD, Cons have ~20 majority
In 2005, labour lead is slashed from 66 to ~40
Scotland has a massive impact on Westminster
Exactly this... Scottish votes have never altered the result of a UK General Election since the 1950s. Not once since then have they mattered because of the number of voters South of the border. Even during the Tory/LibDems coalition, Scottish votes still wouldn't have swung it.