I've done quite a lot of work on properties that have experienced it. Underpinning and structural repairs etc
We had what appeared to be subsidence and it turned out to be a drains issue. It made the difference between a £100 excess on our insurance rather than a £1000 excess.
My parents had to move out for about a year in the early 90's to have work done. Quite a few houses in the area (Smithies Lane) were totally rebuilt. Was all handled really well at the time.
Nice houses down there... We weren't to far away on flaxley road. The houses on that bit and the estate that backed on to it had a lot of trouble.