When you phone you just ask to speak to Open Ride Travel who are the Disney Uk people.
They will then take your details over the telephone. If you tell them you want to pay monthly they might be able to do it differently for you instread of phoning each time

The person I speak to everytime is Kelly who is helpful. Also bear in mind that you need to phone during UK office hours and I have found it best not to ring between 1 - 2 as they seem to be at lunch