I have put this in freebies because thats where I would look for it originally.
I emailed Harrods and asked about the tickets - mainly, what date do they become available. They emailed me back with this:
Thank you for your e-mail.
I am pleased to advise that tickets to the Christmas Grotto will be available to book from Tuesday 22 September. Tickets can be booked online at http://www.harrods.com
and are subject to availability. Please note that we are unable to take bookings via email.
Due to the growing popularity of our Christmas Grotto, a £5.00 administration fee has been introduced this year. All children, babies and adults will require a ticket each to visit Father Christmas.
We would kindly request that if you are unable to keep your booking, please inform us in advance, where we will endeavour to make an alternative booking.
If this is correct and the adults that go with the children need tickets, its going to be a dear do!!