I just came back from Paris & London. I got some stuff in Paris which came up to around 6000euros and some stuff in London.
I queued at Terminal 3, the VAT counter outside check-in. And the queue so long that it stretched outside the airport! After about 20minutes, this guy came around and said he will be collecting the forms from those who have opted for credit card refunds.
So he went around, glance through the forms to make sure everything was filled in and checked our passports, and just took the forms.
He said he's collecting the forms and will be stamping them and mailing them for us.
I'm keeping my fingers crossed that I get the refunds back. The last time I exited from London in Dec last year, I had to queue for about 30mins to get to the counter but they didn't ask to see the goods or instructed me to show the goods to the VAT counter after immigration check-in.