I just called McDonalds now on 020 8700 7000.
And got transfered to the Customer Services Department.
And they said (now at 1.23 pm, it says on my note), that the e-mail address
sometimes work, and sometimes it doesn't.
So we agreed that I would try to send an again a bit later, and have a look and see if the e-mail address is working again then.
So we'll see.