i saw this last week, i too get poor signal at home, but im on three.
I emailed 3 and they rang me back yesterday, they proceded to tell me there were no signal problems in my area, but that for £130+ quid i could get a home signal box. I told them im not paying for it, as with that 130 quid i could just grab a half decent phone on another provider.
they are sending me one free, its coming today, between 3 and 4 pm.
not sure about yours but the three one can have up to 22 numbers stored on the line (for friends and family) but only 4 of them can work at any one time.
the box can be transferred to another address, but you have to tell them, so that they can set it up.