Sweating in nylon? Not being warm in nylon?
If these two things happen you are doing it wrong. Good nylon is for pants, and coats. Polyester is what fleece it, but it is also used for many shirts and some pants. This gear has kept many hikers warm and dry. Pants, shirt, sweater, and wind/rain coat is good for spring and summer in many areas. For winter you want thermal underwear and both fleece pants and sweaters covered by wind/rain pants and jacket. You must layer properly as it is possable to sweat even in the winter, and yes, even in wool clothes. Dead men wear cotton when it is cold and wet outside
Warmth in any fabric depends a lot on layers and wind protection. Clothes do not make you warm. Eating food and burning calories creates heat. Clothing only surrounds you with air pockets to keep your radiated heat in; but on a windy day without wind protection the wind can blow away your heat.
I use wool/nylon mix for socks and sometimes hats. And yes I sometimes wear wool clothes for the charm (at $3 I am addicted to US Army 1951 pattern wool shirts, Canadian Army wool sweaters, styled after your British jumpers, are often around $5)
Wool is ok if you have a car and are just heading to the woods for a day...if you are going hiking for a week or so it gets a tad heavy to carry on your back and hard to dry (compared to nylon). Sparks from flames? Use a cotton jacket or wool shirt if you must and use only hardwoods. I do have an OD 1951 para-parka I love wear from time to time. It is either cotton or a mix, but very windproof.