You could try something like this (untested):
Select HouseLine1 = (case when len(House_No_End) > 0 then House_No_Start + ' - ' + House_No_End
when len(House_No_Start) > 0 then House_No_Start
else House_Name end)
If you haven't even tried to resolve your issue, please don't expect the hard-working volunteers here to waste their time providing links to answers which you could easily have found yourself.