Just adding my experience here as it is very similar to other stories.
We have owned a Kenwood K25MMS12, purchased from Curries for £70 on 4th November 2012. It's 27th October 2014 today, so it seems quite a pattern that these machines pack up after 23 months.
Ours went out in style though... It exploded.
The wife admitted to me afterwards that she did hear crackling coming from the machine on a couple of occasions previously. However, it decided to wait for me to make its final bow...
No metal or anything inside, we had just started it on a cook and it seemed like it was hemorrhaging with unearthly noises coming from inside. I looked inside the window and flames were shooting out from a panel on the right side.
There was then a huge bang, switched off from the mains and stood well back.
Needless to say, our next purchase definitely won't be Kenwood.
Kris Koster, October 2014