Chalet bungalow insulation query

tlj7

We recently moved to a 4 bed chalet bungalow & had a sky light window fitted in our spare room, which highlighted the lack of insulation. Now it has turned colder we are getting mould appearing in our bedroom on the windows and my shoes in our fitted wardrobes. The bedrooms appeared very warm in the summer when we visited so we thought insulation may be an issue, the previous owners had ceiling fans & air conditioning unit!

So what are our options to improve things & who do we get to advise us, we are not DIY people?! Could we look at getting Kingspan boards fitted? Do these fit on top of the current walls/ceiling or between the rafters? We plan on replacing the fitted wardrobes so want to sort the insulation before this but what type of tradesman can advise us - builder, roofer, insulation expert?

Any advice much appreciated and I'm a novice so please be gentle with me...

Many thanks