Quote from blah12345678:
If you're going the 3G route, can you put up tower and antenna in your yard in the general direction of the cell tower? If so, you can just run a coax cable back to your router.
Take a look at this site for ideas. Hopefully you can find a something similar in Europe - http://3gstore.com/products/76_3g4g_antennas.html
Cell towers usually aren't so far that horizon is part of the picture and they are usually pretty high. Line of sight can often be attained without too much height. At microwave frequencies antennas can be quite small and exhibit lots of gain. People have made very high gain, very directional antennas out of Pringle's cans. The investment required to go from no bars to four bars can be next to nothing...