The freeview website says the cable on the lnb should point towards 8 o'clock (if the dish face was a clock). 

I found the best signal with the lnb cable pointing towards approx 5:30. Was using a cheap signal meter and confirmed by signal strength of tv menu. 

Great but I can't help being curious, why would this be. Dish is mounted at edge of roof on one of those brackets that screws into the soffit. Dish is pointed back across the roof towards the apex. Is this something to do with the signal bouncing off the roof?