I've recently just started playing and usually manage to get to the Driving Range twice a week but I've a fairly large garden and was wondering whether it would be worth supplementing my practice time by buying those plastic practice balls...you know those 'Airflo' ones...Are they any good? I realise they're not going to be like the real thing in flight and so on but I was wondering if using them would really help my game.
Thoughts...

I have used them. You are right, they are nothing like the real ball. I got them just for something to hit when I was practising my swing over the field because you don't need to walk far after each shot and a nasty slice cannot do any damaged..

As Joroni says, not much use other than being able to hit something without causing any damage.

Plus practice in the garden leaves divots in the lawn!