Need a really warm, waterproof jacket!

Hello all.

I live off of a motorcycle, in the UK, wild camping almost every night. Winter is soon upon us, and I'm looking to get a jacket/smock that can be used on ny bike, over my armour, and when making camp, something that can keep me really warm and dry.

I'm looking for something completely waterproof, ideally a smock/anorak, so water can't run in through a zipper. And it needs to be insulated, very very insulated. I sometimes ride in temperatures below -8°C (17.6°F for my US friends) factoring in wind chill, it feels much colder, and as riding a bike isn't a physical exertion; I don't produce nearly enough body heat to warm me. Breathability isn't much of a concern, as exertion isn't a factor. Layering only works so well, and eventually my body will have all heat wicked away, and the amount of layers becomes cumbersome... A lot of bikers use electrically heated apparel, for reasons I won't waste words on; this isn't an option for me.

My military friends recommend the Keela SF Belay Smock. Some of my hiking friends recommend arctyrex jackets... I'm rather curious as to what people wear in the Arctic, or at sea, on oil rigs etc.

I'd like to put this out to all the helpful people on Reddit, thanks in advance for any advice :)