No socket within 3m of a shower or bath inside the same room, except for a special type intended for a shaver. Note the "in the room bit". I have a socket about 300mm from the edge of my bath, but it's just outside the bathroom door.
If your existing socket is at least 600mm from the outer edge of the shower, it can be replaced by a FCU. This assumes that your shower is reasonably conventional, and not an open wet room type with horizontal jets as well as vertical.
You can Google "bathroom zones", but about 90% of the diagrams you will find are incorrect. There is no zone around a hand basin, and zones 1 and 2 extend to 2.25m from the floor (whatever height the bottom of the shower or bath is), and the area above that is outside the zones. Your FCUs must be outside zones 0,1 and 2.
Edit: Just spotted the diagram. Anywhere the other side of the WC from the shower is OK for the FCUs, which must be 30mA RCD protected.