I'm looking to have data as a part of this too -- and local calls within the UK. Potentially some calls to Germany/Poland/France etc.
That's why the 20GBP is appealing for 600 UK minutes + Data and I can figure out the international fees from there.
I have several cards with large credit lines (including a corporate one) so if they need to put a hold on that for a bit, its fine for me.
-W