You have to differentiate in between Astra 2D and the rest. For latter i cannot tell you for sure but roughly expect to get everything on 2.40m, probably also on 1.80m, always quality dishes (I'd be careful with MABO, have heared some negative things lately). First is rather chaotic and differs from place to place but be aware of something extremely big.
My recommendation:
Ask some shops that are experienced in UK TV installations all over Greece: _http://www.satellites.co.uk/satellite/835327-post13.html
@geoffreys:
Does the 4.2m receive anything off 2D ? If so i'd be interested in which frequencies are beeing received and if so 24/7 or not.
With this size, it would be a shame if there are no other LNBs for 19.2E/23.5E/26E installed as well. Suppose that there wouldn't be any problems in receptions as well concerning Astra 1F and Badr 6. For Astra 3A i'm not that sure.
As far as i know in greek towns (on the countryside you can do whatever you like) you are allowed to install any dish size on your own roof as long as the height is not over 4m. You just get to the Poleodomia (authority for building) and get such an A4 document. A lawyer wrote about this in the greek sat board SDTV some years ago.