The UK free to air channels are broadcast on a sattelite with a narrow beam that is only intended to cover the UK. This means if you are a significant distance from the UK you will need a big dish.
Here is a map with approximate dish size requirements http://www.sam-radford.me.uk/astra2d.htm . Unfortunately they don't even specify a dish size for greece but looking at the trends on the map we are talking a size measured in meters .
Give satcure a call (http://www.satcure.co.uk/). I believe the owner lives in greece or at least owns a property their so should be in an excellent position to give you some advice. I have no relationship with the company but I remember seeing some things he wrote in the monthly newsletters they produce.
You bounce the current signal from a different signal, I used to get Filmnet, german porn tv, via decoder, in the erly stages...there are many more satellites up there now....adjust the dish a little...and get more channels?