Width. Depth. Clearance.
Small homes are not solved by buying more objects. They are solved by choosing things that survive the boring measurements: width, depth, height, clearance, door swing and daily movement.
The Tiny Flat rule
If an object blocks the route, catches a door, needs fixing you cannot do, or hides the thing you use daily, it has not earned its space.
Width
Measure the usable run, not just the wall. Skirting, sockets, radiators and handles all steal space.
Apply to hallways
Depth
Depth is the number that usually breaks a small flat. A 10cm difference can decide whether a route still works.
See narrow storage
Clearance
Drawers, doors, lids, baskets and wheels need movement space, not just storage space.
Check under-bed storage
Installation
Freestanding, adhesive, over-door and screw-fixed storage all behave differently in a rented flat.
See renter-friendly options