Hi Kerry,
It's always lovely to be able to answer a question from a fellow Brit!
You can begin making your
Advance Dining Reservations online at 6:00 AM EST (that's 11:00 AM GMT here in the UK) at 180 days out.
If you want to make your Advance Dining Reservations by telephone, you can do so by calling 0800 16 90 748 but, if you do choose this method, you will have to wait until 7:00 AM EST (that's 12:00 noon GMT here in the UK).
I personally find it easier to make all of my Advance Dining Reservations online and as an added bonus, you will get a 1 hour head start if you choose to do so.
It's also worth noting that if you will be staying at a Disney Resort hotel, you will be able to make Advance Dining Reservations for the first 10 days of your stay at 180 days out. (Do however make sure that you have linked your Disney Resort hotel reservation on My Disney Experience beforehand.)
Wishing you a magical holiday filled with memories which will last a lifetime!
Emma