I sold some via Locostbuilders for £60 about a year ago - but they seem to go from anything from £20 - £80 depending on cost...
I think that, certainly with the Locost rather than the Haynes, there are specially made uprights that match the geometry but which are better. Racelada as a 'brand' rings a bell in my mind - e.g. see here:
http://www.locostbuilders.co.uk/view...php?tid=105874
Might be more expensive than donor Sierra/Cortina bits - but presumably lighter and better for the job...