Yes, the wording matters. However, if (as in the example I illustrated)that wording says "£5.00 (was £14.37)" then I think that is clear and, when that is 'said to' the entire general public (i.e. with no 'conditions')1. will; be interpreted by most people as "a sale"
Agreed, unless they first sell the item for more than the 'second sale price' for a period of time (28 days?). However, that prohibition would presumably apply to a claim of "(was £100)", "discount of £xxx" or "discount of xxx%" just as much as it would to calling it a 'sale'.
They are obviously free to move the price up or down, by any amount, as often as they like provided they don't makes claims. However, the moment it is called a 'sale' or a 'discount', it's surely necessary for them to be able to demonstrate that the 'sale price' or discounted price is less than the price for which they have recently been selling it, isn't it?