Rob,
I bought mine from eBay (from nicholas2528, Ozzy1's, third link:
http://cgi.ebay.co.uk/haynes-roll-ba...item23105041a6)
Mine was more than £50 but it did include the rear stays, nuts, botls, and the rear stay fitting plates. It was well made, accurate and well packed, I would recommend him (he's ntdwm).
I think his price of £50 is good, you might get it cheaper if you wait for a group buy, but I think there has just been one.
EDIT: Opps just realised you've posted that you'd bought it, while I was writing this.