We had problems with chimney draw and added a cowl, haven't had a problem ever since. The more I hear about your heating maister MW the more I believe he hasn't been doing it long
Everybody wants to have a dig at my Bulgarian Heating Engineer/Plumber.
He is fine, he worked in Israel so I guess he is more Solar orientated than wood burning stove. However, see Lilliana's post above yours. Not everyone likes the cowls for differing reasons. I'd rather read other folk's opinions before splashing the cash and finding out for myself.
Perhaps you don't get much wind where you live? We get strong North Easterlies to North West winds most of the time, (50 KPH now and again) and in April/May we tend to get winds from the East and the Black Sea (can smell the salt on the air). Rarely get southern or western winds and when we do, it is usually not wood burning stove season. I do take notice of the wind especially when wanting to light the stove and it changes my process of actually starting it. When the winds are high from the North, I'll add more fire lighters, paper, prep the chimney with some burning paper and get a small roaring fire as quickly as possible before adding logs. When there is little or next to no wind, I can build the fire as high as I want with dried sticks and it will suck in the air and burn up - no problem.
I will add a level or two to my chimney next year, (easy enough job) but if I am going to go down your Pellet Boiler route in the future then, there is not much point as that would be situated in the nearby boiler room/house where all the utilities are located.