If the shy Tories don't turn out and Reform gather some momentum there is a non-trivial chance that the SNP could become the official opposition.
However, I think it is more likely the Reform vote collapsed close to the election. The Tories will also play up immigration, despite them being responsible for the highest immigration levels ever, they will paint Labour as weak on this and gain some votes. The Tories won't be in a position to win, but I would be very surprised if the don't get more than 80 seats.