i was right, and this is a non-standard Playfair cipher. Pairs of letters in the same row OR the same column both get shifted vertically, rather than using the left right rule on a row. It took me a while to get that, and then to work out whether the shift was up or down!
The other thing to note is that they used zero as a separator to split repeat letters, presumably because there are no digits in te actual message itself. Here is part of the grid I worked out as a new Year’s gift! Harry