Well, super efficient Ocado have emailed me back already:
Dear Mrs Flashing Nose,
Thank you for your email.
Christmas delivery slots are being allocated by postcode and frequency of shop and we have not opened delivery slots in your area. Please be assured that you will receive an e-mail advising how and when to book a delivery and also make sure to keep an eye on the website for your addresses delivery slots. I hope this helps.
If we may be of further help, or if you have any comments or suggestions about our service, please telephone us on 0845-399 1122 or, alternatively, e-mail us at [email protected].
Yours sincerely,
Ocado Customer Service Team
So there you go!