First off Are you planning an all glass conservatory or a sun room
A sunroom would be better as it would allow you to use it all year. A sunroom is basically a block construction to certain height and significant proportion glazed from here up. A normal roof is then installed. With this construction it would be a nice comfortable level all year round.
As for the triple glazing, not much point unless the rest of the house is highly efficent even then it wouldnt be top of my list. With triple glazing comes expense weight and size. In my opinion a Double galzed unit would suffice. This unit could be highly insulated and have a low e coating which would surpass the triple glazing(assuming its standard