I live in switzerland,
in the UK, is the problem you are having that the bulbs dry out in summer or rot in winter?
canadense needs quite a dry winter, ideally covered with snow and without too much moisture. In summer however the bulbs resent drying out.
I finally had sucess with them planted in a spot where they get sun from 7 am to about 10 am and then evening sun from about 5 or 6 pm which they love. I plantred the bulbs quite deeply so they would not suffer from our very hot summers, in a very well drained mix made up of 40 % humus, 30 % pine needles and the rest a few bark chippings, aquarium grit and normal garden soil. I grow my fritillaria camaschstensis in the same spot band they seem to like these conditions as well.
I have a friend in the Uk in northamptonshire who grows canadense sucesfully in ericaceous sandy soil in half shade in deep pots plunged into the ground.
in the wild, in canada, canadense grows along streamsides, so does get quite alot of moisture in summer, but is quite dry in winter as its then covered in snow.
in gothenburg botanical gardens they grow both forms very sucesfully in raised sandy ericaceous peaty beds in half shade together with pine trees, lilium grayii and lilium paryii