Ok... after some thought I don't think they can cancel in this way (or the rest of what I have done wouldn't make sense).
Anyway, instead of writing everything out in full, I'm basically working the Lagrangian on page 5 of this source http://www.phys.columbia.edu/~kabat/susy/susyQM.pdf and...
I've been tasked with showing that a Lagrangian under a set of transformations changes by a time derivative. All has gone well, except I'm left with two remaining terms, that I am completely confident, aren't there by mistake (as the 16 terms that should be expected have all popped out with the...