I used Barbour waxed cotton jackets for years Neil....my uncle was a friend of the company owner
They are very effective in keeping the rain out, VERY waterproof. However, I lost count of how many times I sweated my dooda's off re-waxing one jacket or another with an expensive tin of Barbour wax, a cloth to rub it in, and the missus hair dryer to melt it and insure it penetrated. The problem is, water proof they may be, but they most definitely are not breathable...so you can sweat badly and get just as wet that way. They usually have ventilation to help with that, but it doesn't fully prevent it.
So, Barbour coats basically have the same problem as a Goretex that has lost it's 'beadability' and is not performing correctly as a result. It doesn't breath, which means you sweat....which is why they have have become far less popular as the new fabrics were developed.
There are other, newer fabrics coming onto the market which apparently don't work the same way as Goretex...but they are very expensive.
Cheers, Dave.