I've just gone to do an order and it's telling me one of the items is an "add on" item and I need to order £20 of eligible products for it to be sent! 
Problem is I can't seem to figure out which items are eligible. There are other things I need in the order which aren't eligible but if I can find suitable alternatives in the eligible products I'm happy to swap.
Tried loads of different search terms and getting nowhere!
Help!