So four years at a Scottish university costs the same as three years at an English one?
The fees cap is political whitewashing. Fees go onto a student's SLC account, which is the softest money you will ever borrow, and simply alters the balance of whether you ultimately repay it all or not. Even for a relatively well paid graduate, the years in which it will alter your repayments will be your 40s.
However, for parents who are not in very low income brackets, the main issue is the immediate, right here right now, cash outlay for maintenance requirements over and above the maintenance loan (which, in passing, also isn't capped). So if your view of the realistic cost of a student living to a standard you are happy to fund them at is (say) ten grand a year, then it's going to mean an additional five grand SLC maintenance loan (same point as above) and, more importantly for the parents, an additional five grand right now (or, more accurately, in four years' time).
From the point of view of the outlay from the parents then, assuming you are not eligible for income-related additional loans, a four year degree costs 33% more than a three year degree wherever you do it, because it takes 33% longer. I realise parents with children in the process of applying are terribly exercised about fees, but I find it depressing the number of parents I've met who appear completely startled at the need to help fund living costs.
All the points about the differences between four year "masters" undergraduate courses and a bachelor's degree plus a specialist masters are well made: the main reason for the existence of four year undergraduate "masters" in STEM is the requirements of some professional bodies for faster routes to CEng.