Here are my findings based on two locations in Scandinavia.
4 kms north of Oslo, Norway - CH4 HD on a 80cm dish is OK in all weathers. LNB is sky's "standard" 4 way LNB that came with my original - now defect Thomson HD receiver. No brand name on it that I can see.
20 kms north of Torsby, Varmland, Sweden - no signal on CH4 HD on 95cm dish. LNB is a triax 0.6db twin.
Astra 2a/b and ch5/itv on 1n are fine in both locations, Astra 2d I've never received.
The Swedish location is 160km from Oslo by road, maybe 130km east as the crow flies.
Same receiver used both locations (amstrad 1tb Hd). Cable run in Sweden is 20m, in Oslo 5m.
I've ordered a new LNB for Sweden - platinum 0.2 DB I think it was, will report back when I've tested after Xmas.
Regards, PJ