There is an illustrated step-by-step description of the Heliochrome process
in the current UK weekly, Amateur Photographer (8th April '95, pp 50-52),
from which it appears that the modus operandi is very similar to gumbi. The
kit (containing paper sealant, activator and six toners) costs 45 UKP
(enough for 15 12x16 inch prints) and is obtainable from:
FilmPlus
216 Kensington Park Road
London W11
Tel: +44 (0)171 727 1111
Dunstan has been researching this process for many years, and although I
have not used it, the results I have seen are very fine.
I should add the usual disclaimer that I have no commercial interest in the
sale of this product.
Mike