Floors and ceilings mostly. Although we build walls in masonry, we tend to use suspended wooden floors rather than poured concrete slabs. This is one reason why we popularly DIY install floorsafes, not wall safes (other way round to the USA). Also drywall cladding is needed for any penetration of the bricks, including around plumbing.
So when your adjacent garage / workshop roof leaks, there's a few inches of rockwool to soak up the insulation, then a few layers of plasterboard. By the time you even notice, it's a right old nasty mess up there. Guess what tomorrow's job is? 8-(
If you have a _major_ fire in a UK house, it's almost always because the fire has got into a roof or ceiling void and then spread that way. Room fires are generally survivable (if you're elsewhere and leave), multi-room fires are the ones that kill families (we've had a bunch of them lately).