good website there rik, only problem i can see is none of the sleeping bag manufacturers are willing to give a season rating for the bags.
my eldest has the vango nitestar midi which is rated between +7 and +20 and i'm guessing that these other bags would be about the same. he has'nt complained yet about being cold in the night but i am going to invest in a fleece liner for his bag and i'll do the same when i buy one for james.