This sounds like a situation where you might want to look at Booster antennas and the quality of your equipment. I have an old Sierra 551 that I purchased off E-bay with good reception and more importantly the ability to be hooked to an external antenna. Something like that with a Cradle Point router might get your farther if you are mostly working from a stationary location. Put an antenna on the roof, run a cable into your place and feed it into a wifi signal covering your area.
In the US, one of the best suppliers of this stuff is Wilson Electronics. I'd be curious if there is a comparable company on your side of the pond.
Cell Phone Antennas and Cell Phone Boosters at Wilson Electronics