How much bandwidth does iTunes Match use?

I signed up for iTunes Match in the UK last night once it went live and it's apparantely whizzing away matching my songs (although it appear to be stuck on the last one). As, like most people in the UK, I'm on a very limited bandwidth broadband account, I'm worried about the possibility of it trying to upload and download several gigabytes of data in one go as it runs a serious risk of either maxing out our montly limit or pushing it close enough that I can't upload/download anything major for 30 days. I'm lucky enough to have a 100gb a month limit, but typical UK accounts kick in at 5gb as strict limits or 'fair use' hidden ones before speeds get dropped to dialup.

Does anyone know how much data gets uploaded/downloaded? Also, suggestion for the iTunes Match team. Give us an option for iTunes Match (and iTunes generally) to wait until user defined 'off-peak' hours to do any large transfers as accounts like mine are unrestricted between certain hours (usually when we're all asleep).