Moving router downstairs

Our router was installed in a bedroom upstairs which I used as an office along with 2 telephone junctions boxes. Having been retired for a few years (and before getting the hall and stairs decorated) I am thinking of getting the router moved to the bottom of the stairs to get rid of all the bulky cables that go up the stairs. Also I would like the old telephone junction boxes removed. 
I am a little hesitant to go ahead with the move as we use a PC in one of the other bedrooms and a laptop in another one. Both these get good signals at present although our TV signal downstairs is very poor. Is there any way we can check what the signal would be like if the router was moved? The cable is not long enough for us to do it. Also I understand the call out charge is £25, are there charges on top of that depending on what needs to be done?