Get yourself a new dish (Triax is a good brand) - 85-90cm. At the same time, buy a 'multi lnb holder' (lnb is the yoke out front pointing at dish). Again, Triax produce holders to fit their dishes. You can then have up to four lnbs working off the same dish ie. 13*E/16*E/19*E/28*E - or less as required. Obviously, the requisite number of additional lnbs needs to be ordered up together with some ct100 sat cable, some twist on connectors that fit said cable, and a diseqc switch - so that you can switch between satellites. Also, you need to check that your box supports diseqc switch - may not be the case with a sky box.
Hope that helps.