Training in the cold

Back when I worked in a bike shop and it was cold, my solution was to train either late in the morning or afternoon. But most of us have a full time job that doesn’t allow such luxury.
Another solution I have tried is to rug-up really warmly and go out in the frosty dark of early morning. With good clothes it is possible, but it is rarely fun. I also find heart rate and power levels are out of the normal range due to cold air and hot clothes.
For the past few winters, my solution has been the stationary trainer. There is no wind on the trainer so even though I am outside, I am not cold the way I might be riding.

Several of my riding friends have been doing the Zwift thing. In case you don’t know, Zwift is an interactive online virtual training web based program that allows you to ride “with” people from around the globe, together (in London, Virginia or an island in Micronesia). Zwift requires a smart trainer that can alter the resistance according to your position in the peloton and the slope of the hill you are on.

Smart trainers are the new “thing”. The Tacx Neo can even spin your rear wheel for you as you coast down a hill, and it can provide the pedal kickback you get on rough roads (cobbles, cement joints, even gravel).
I want to use a smart trainer to make my interval sets more accurate, but I’m not really drawn to Zwift at all. Smart trainers have an “erg” mode where it locks in the power output of the rider - slow pedalling requires a very high load while fast pedalling requires far less load. It if exactly unlike riding on the road - no matter how fast you pedal you go exactly the same speed.
At around $1600, it is a lot of money just to have good intervals.
In the meantime, I am borrowing a smart trainer so I can try a couple of weeks of this type of training.