You are lucky with the customs limits (or not) in the UK. Here the limit is 22€ and it is very rare that something 'sneaks through'. As for the duty charges, they make them up as they go along, so I always try to make sure something is EU-based before ordering. I've lost a couple of things to the scamming so & so's, just not worth the money/grief.
I often wonder if Germany has some kind of agreement with China, as a lot of stuff seems to ship from there at much the same price as advertised from China.