
No there is a better way - and one which is more subtle and adds to the point you have already made.
Point out that the £2 coin has proliferated in the last year; ask them when they last had a fiver and point out that there are clearly more £20 notes in circulation than £10s. It is very hard to argue against, especially when you list rises in: fuel, food, general groceries, gas, electric, water et al to go with it.
All of this is sure-fire, recent proof of major inflation!