So, I started to reload .303 with a Lee Loader. Here's my experiences:
First of all, it depends on what you want to shoot your .303 for. If making a big noise, giving your gun a workout and so long as the shots get somewhere near the point of aim is your goal, it's ideal.
I did a good few rounds with mine and never had a mishap. If you are meticulous and concentrate, it's perfectly safe and produces viable ammo. However, there are drawbacks. It's noisy, if that's an issue. If you use the yellow measurer for your powder, you are only going to get the right amount of powder per round occasionally and randomly. Although for plinking, that, you might conclude is good enough. It does only neck-size. Which isn't such a problem with .303, so long as you use the ammo in the rifle it was fire-formed in. However, obviously as you use the brass a few times the length of them will grow, so you might in any case want to acquire a solution for that.
It isn't that bad and is a quick way to get shooting your own rounds. But if you intend to use your rifle on an ongoing basis, then a nice, not too expensive single stage press and a set of dies won't break the bank and is probably the better way to go. You will likely end up doing that anyway. You'll probably end up getting a nice, not too expensive powder measurer or some scales, maybe a case length trimmer and other bits and bobs too. You can pay a fortune, but for around the £100 mark you could get up and running with a press.