I have a 4m bell tent and totally agree it would be a bit of a squeeze for four adults with a stove fitted. Its a bit of a squeeze for my wife and I and our twins who are eight. They are a lot of money but cared for correctly they will outlive many a nylon tent. They have great stability in the wind I have used it in all weathers and never had any water come through, not one drop. If you wanted to fit four adults comfortably I would go for a 5m if your budget allows, mine didn't. If you do get one make sure you dry it correctly otherwise it will go mouldy. I dry mine after use over the banister for a few days and keep turning it.
Another thing to consider would be the groundsheet style you would prefer, I went for a separate ground sheet as it is easier for me to dry out the canvas. You can get attached groundsheets and zipped in ones. Good luck.