Have a large sunroom of the kitchen also, original as a dining room, now a second sitting room, my advice would be top spec insulation and excellent glass,
last christmas we put in double doors (full glass) with side fans and three overhead windows separating the kitchen and sunroom as the temp in the sunroom was considerable lower in the sunroom, at the cost €1525 to buy the doors/pieces plus the price of handles/hinges etc extra (€75) and also it took three days work to fit (thankfully free as we did it ourselves).
Also seen a glass company in paper offering tripple glazed glass that replaces your double glazed glass by simply fitting into your old frames.....
Better to get it right at the building stage....