The trouble with Combat Jackets and Duvet Jackets (like the Snugpak) is that they are a bit "All or Nothing."
You are either wearing them all the time, regardless of wether you are Hot/Cold/Wet/Dry, or you have a massive lump to cart about.
With your budget, I would look round the Charity shops for a couple of Decent Fishermans or Army jumpers (Wool ones) especially now while they will be dead cheap!
To go over the top of these, you could do a lot worse than a British Army Jungle Shirt (if you don't mind DPM- and you can dye it black if you do).
You can get one for around a Tenner, if you hunt around the surplus shops on the web.
This will do as a windproof and is fairly good round fires.
For very heavy rain, buy any old lightweight P.U. Nylon Waterproof that takes your fancy and wear it over everything else when you need to.
This will give you more control over how hot your clothing is, and is called "Layering ."
It is the same method used by the Inuit and Lapp's and has been adopted by Mountaineers and Kayakers, although modern gear is all Synthetic- so prone to spark holes from fires.
The only difficulty, is finding stuff that can handle the odd spark without melting, but you will find your own ideal set-up with experience.
