Tesco/Mysupermarket: How to update a Christmas holding order

A question about : Tesco/Mysupermarket: How to update a Christmas holding order

From 27th November, we get to put holding orders in with Tesco for Christmas delivery slots.
I use mysupermarket for all of my Tesco deliveries.
Year after year I get tangled in knots with my Christmas order trying to update my holding order in mysupermarket, the day before delivery, with what I really want delivered on the Tesco website.
Has anyone worked out how this can be done efficiently? (I seem to always end up having to do my order in MySupermarket, and then manually doing it in Tesco from my Mysupermarket shopping list.)

Best answers:

• Looks like manual adjustments it is.....
  Just booked my slot for Christmas Eve - don't forget to reserve your slots - looks like its filling up already!! (Only released today)
• hi, hope you don't mind me butting in!
  ive been checking daily to book a xmas delivery slot, and no dates are on yet (just checked) for after 19th Dec? am i missing some thing?