Dreams

We are definitely on clay but not a terrace and already 3 storeys high. I am told we need to achieve a head height of 2.1m, which means an extra 30cm. Are foundations likely to be adequate? Anyone?

Is there some kind of test that has to be done to check if foundations are deep enough?

We are just thinking about doing our cellar too. Smallish room 3.5m*3.5m proper tanking job to a usable room with a window. Will need some digging down (30cm) to create headroom. Does anyone have an idea of how much this is likely to cost?