Another part is that many people buy on price; that coupled with inflation means that manufacturers who want to keep supplying an item at a given MSRP have to produce them ever more cheaply, thus often cutting corners or switching materials.

http://www.manufactum.de/ is a company that tries to reverse that trend a little; their tagline is "Those good old things still exist", and they specialise in selling things manufactured (often in the literal "made by hand" sense of the word) in traditional ways: sturdy products that will keep for years if treated properly rather than falling apart just after the warranty expires.

I don't know whether they have something like that in the UK, though.