I think you get a lot more than 3.5 these days. A single applicant might be able to shop around for a multiple of 5 or even more. Couples get less, but even 25 years ago, when I first bought a place, myself and my g/f were offered much more than 3.5.The average salary in the UK is £27k. To get a mortgage on that, x 3.5 = £94,500. Let's say you even have 10k deposit, that's a £105k house. How many new builds are being built across the nation that have that kind of purchase price?
Not sure that's a good thing, as it probably drives prices up even higher.