IMO you can't beat a Weatherbeeta Combo for fit, durability and they come up like new wash after wash. My grey show cob wears one after every bath and they're washed every time they're used - I have 5 now (!) and the oldest is probably 7 or 8 years old!
Thicker fleeces are available however IMO they are not as durable nor the cut so generous.
You could perhaps consider the Snuggy hoods (I will only use headless ones after seeing several friends horses get eye injuries from hoods with eye holes) as the extra layer - they often have sale items for 60% of the full price. Their fleece is thicker however they're obviously more of a pain to fit as they have a belly flap.
I had the weatherbeeta fleece combo and the fit was awful. All his other weatherbeetas are fab too, even the standard fleeces. I opted for just a standard fleece and bought a neck part (snood) online that goes over his head .
I was also going to recommend the Swish one, saw them today at YHL and was extremely tempted - if she didn't already have 5 fleeces then I would have had to get it! Looked lovely and I've been very impressed by their other rugs.
I absolutely love the derby house combo. All their rugs fits my horse like a glove and because they are relatively cheap I don't mind when he destroys them. His fleece is pretty good quality, obviously not that of thermatex but it doesn't feel cheap.