IP ratings are the single most confusing thing in domestic lighting, and they need not be. There are two numbers, and for a bathroom only the second one really matters.
In short. Zone 0, inside the bath or shower — IP67 · Zone 1, above it to 2.25m — IP45 · Zone 2, within 600mm — IP44 · Beyond that — no rating needed
What the numbers mean
IP stands for Ingress Protection. The first digit is protection against solid things — dust, fingers. The second is protection against water. In a bathroom, the first digit is almost never the constraint.
So IP44 means reasonably dust-protected and splash-protected from any direction. IP65 means dust-tight and protected against jets of water.
The zones
Zone 0 is inside the bath or shower tray. Almost nothing goes here, and what does is low voltage and IP67.
Zone 1 is directly above the bath or shower, up to 2.25m from the floor. IP45 or better.
Zone 2 is the 600mm band around Zone 1, and around a basin. IP44 or better. This is where most bathroom wall lights actually go — either side of a mirror above a basin.
Outside the zones, more than 600mm from any of it, there is no IP requirement at all. A hallway wall light is perfectly legal beside a bathroom door, and often beside the bath in a large bathroom.
Why this matters
Because most people over-specify. If your bathroom is big enough that the light sits well away from the bath, you are not restricted to bathroom fittings — and you have the whole range to choose from.
The honest caveat
Zones are defined in BS 7671, and how they apply depends on the shape of your room. Every product page here states its IP rating and which zones it may be used in, but your electrician should confirm the zoning for your bathroom before anything is fixed to a wall.