My experience was that it went from bad to worse very fast. I think it was a matter of the jiggle that broke the laptop's back.
The screen could be related to the power problem. Stripes could be a power surge (or dip), which goes back to the cord having to be in weird positions.
At the same time, though, it could be more serious, especially if the power supply was giving off so much heat it was melting cables.
£100 is about what I'd guessed the going rate would be (and still several hundred less than a new laptop!). It sounds like they're better prepared to deal with the problem than the first one.