You can buy buildings and contents insurance separately. Contents insurance shouldn't care about subsidence, as that's a buildings issue I would have thought
Our house is quite near a water way as the crow flies, but the elevation and location mean it's fine. However, there are a few insurers who just do a how many meters appraisal. Which rules them out. It's just the way a particular insurer sets their criteria.
We can't insure your bikes as your house might crumble to dust is a new one.
R.e. subsidence it would have come up in the Solicitor bsearches when you bought the place if it was a risk