Sorting Parameter values in SSRS Model based report

I've found a tricky, but easy way to do this (if you have control over the model):

1. Set DiscrourageGrouping to FALSE on the field you wish to sort by
2. After adding the field to the data set, drag it to the Left to create a new group based on this field
3. Voila, it now sorts by that field!

Cheers!

Curtis.