Ehm, can you confirm that you get BBC1,2,3,4,Ch4,Ch5 and ITV1-4?
Those channels are all on Astra 2D, which is much weaker than the others at 28.2E for reception Oslo.
Now, You and I at about the same roll-off point for signal strength from Astra 2D (I'm in Eastern Denmark).
I have tried 90, 120, and 180 cm dishes - and only the 180 gives watchable results.
Most people in the near vicinity seems to have similar experiences (note that reception in Stockholm is a signal anomaly).
So considering you're behind a tree makes reception of 2D on Olso on a 70 cm Clas Olsson dish no mean feat.
In any case: SMC dishes are more rigid than (most) metal dishes (they don't flex or bend).
They are also more expensive, tend to weigh much more, and a bit more fiddly to mount.
Most people seem to get best results with Channel Master/Andrew/ASC/Skyview SMC dishes. There are other manufacturers, though, I can't say which one's are better or worse.
Check our the "member's installations" part of the forum for examples. (They're the ones with clear support ribs molded into the back of the dish, if you look at the pics on this site.)
Don't get me wrong: Metal dishes are also good - but you need one that comes in one piece and is high-precision. Avoid the ones assembled from petals (e.g. Fortec Star 180), they are made of thin steel, the assembly means they don't perform anywhere near a good one-piece SMC or spun aluminium, the mount is terrible, the whole thing rusts fast in Scanwegian weather, and you'll just end up being frustrated. I know, because I started with one of those...
I don't have any experience with flat dishes, but AFAIK, they don't come in sizes or effeciencies anywhere near what is needed for fringe reception, so they are not really of interest.
But yes, they do look more discrete.
