I took your suggestion and it worked exactly as I had hoped. Thankyou.

GHCI (6.8.2) was though a little concerned, and told me
I had an: Illegal instance declaration for `ZOT [x] [y]'
and recommended I use -fallow-undecidable-instances. I did,
and it worked. What have I done though? The word "undecidable"
scares me a little :)

---SNIP---