Youll never get a 120mm holesaw much cheaper. And do you even have a pillar drill to use it on?
Only thing with tin snips is that they tend to bend the metal slightly.
You could also consider picking up a cheap jigsaw, (like £15) with some metal blades and just thrash the live out of it, lol.
We did that for the kitchen worktop at our old place. It then died on us shortly after, so we got a full refund