Sorry Mr M, Scarface is right, the charge (certainly in Scotland) is attempting to Pervert the Course of Justice. The key word is 'ATTEMPTING'.
Whether or not you're ever found guilty of it is another thing. I would suggest that it is the sort of charge dropped in favour of another, i.e. a deal prior to trial.
Attempting to Pervert is a Common Law crime and its sentence depends on the court it is served in.
The lowest court in Scotland, the District Court, can sentence you to up to 3 months jail and £3000 fine, if memory serves me right. You'd really need to p*** off the Justice to get that !!