Hi Nigel,
To make your advanced dining reservations, you will firstly need to go to the Walt Disney World website, click on 'Where to Eat' and then 'Make a Dining Reservation' The link can be found
HERE
At the bottom of the box, you will see that it says 'I want to use my dining plan to book reservations'
When you click on there, it takes you to a page which is titled '
Confirm Your Walt Disney World Reservation' You will then need to fill in your Confirmation Number, Last Name & Arrival Date.
Once you have done this, you will not be required to pre-pay for any of your advanced dining reservations. You may be asked to provide your credit card details to guarantee the reservation. In this instance, your card will not be charged unless you fail to show up for the reservation and have not cancelled it within the cancellation policy period.
I would highly recommend that you make your dining reservations at your earliest possible opportunity.
If you have any further problems, I would suggest that you call and speak to a Cast Member on 001 (407) 939-3463 to make your dining reservations.
(To keep costs down when making international calls, you can ring 08448-610-610 and then when prompted, enter the US dining number which I have provided above. Your call will then cost around 1p per minute which is much cheaper than a standard international call)
I hope that this information has helped and that you manage to dine at all of your desired restaurants!