Rothenberger Pipeslice Tube Cutter 15mm £11.93 Delivered @ Plumb2U / eBay

Solid price if you want the rothenberger one 👌

I have one of these. For tight spaces it works great. Doesn't take much effort or many turns to cut the pipe. Doesn't wander off the cut. Leaves a nice beveled edge on the outside of the pipe. Well made from metal and replacement blades readily available.

Though it does leave quite a prominent lip on the inside of the pipe which you ideally should to use a reamer to remove (more so than happens with a cheap manually adjustable cutter I have). Saw other people on forums mention this too so it seems quite common. Not the end of the world, just takes a bit more work to get it nice (I suspect a lot of professional plumbers using these don't bother but they probably should).