This might be a stupid question but I've spent my whole life so far just buying based on what they look like and price. Now I actually care about being WARM. But when I look at what jumpers are made of its rarely 100% wool. Do I need to buy 100% wool? If not, what should I be buying? Half wool, or a cashmere mix or...? I can't believe how expensive some nice stylish jumpers are that are still made of polyester! Or is a polyester mix ok?!