Has anyone got any idea how much of my download allowance Tv Catchup takes up?

Got 500MB per month which I fear will be about an hour of this!

If you only have 500mb i would stay well clear of tvcatchup.
Reset your usage then try 5 mins of tvcatchup to see how much you use

I worked that it was using 2-3mb per minute for me. But that was only over a short time. Probably eats up more. I only use for brief viewing over 3G.

i was using this during the world cup and one match would eat up a few hundred MB's so if you dont have unlimited data usage id be very careful with this. Luckily i signed my new contract last Feb so i still have the unlimited data usage so dont have problems with going over any limits or extra charges

500 Meg isn't enough to watch TV catch up really, you risk eating up your allowance far too quickly.

Though if you are stuck 500mb would cover the occasional half hour as long as it's not that often. It's a great service, part of the reason why I will be joining T-Mobile is because they will not charge if you go over your "unlimited" 1GB, only warn you