I got some from Aldi in the autumn 2017 if I am right. In my experience to thin. (In one layer.)
And I managed to make holes in it by pulling it down. Even after I understood the problem. One moment dreaming and I got the next one. A bit itchy.
Now I use the currently sold 190 g Decathlon Trekking base layers with zipp collar the whole winter and while moving in conditions around 0 to -5*C they are comfortable. Non itchy!
I wear a thick military cotton shirt over it, sometimes a cotton T-shirt under it, and a thin woolen pullover with V-collar over it and a 450g quilted plastic filled plastic Jacket on top. Over it a light water proof jacket.
At the legs Decathlon 190g merino base layer and normal polyester cotton mix trousers over it, Decathlon Steppe 300.
I think the more expensive Icebreaker base layers are meant to use like that. I have the impression that you can wear them under normal clothing in heated rooms and on the way to the office with additional layers.
I have no problem to sit around in a heated room with it.
In one youth hostel this winter there was a problem with the heating in my room, what I discovered late in the night. My clothing where OK to sit around at perhaps 5 *C. But this was the comfort border I guess with that layer system. And don't forget: I am working every day outside! I am used to cold weather!
If I would like to walk between -5C and -10C I would think about to invest in Ulfrotte Woolpower 200g base layers.
Hunters who usually sit around use Ulfrotte Woolpower 400g base layers. That would be perhaps a nice thing for your next year winter camping meeting. But I guess if you can't open it, it would become to warm for normal use and times if you are hiking.
I have a contact to a young man in Hamburg, I guess nearly southern british weather, but always windy, who uses the 200g base layers and the 600g Cardigan and is very convinced about it.
Woolpower 200, 400 and 600 has instead of the competition a sling inner side that traps more air in.
But it is ment to wear it under something else. In the bush you can pull threads out of it, if you don't pay attention.
Unfortunately I couldn't reach my Aldi base layers when it was cold. It would have been interesting to pull it under the Decathlon base layers instead of the cotton T-shirt to see, what's going on, if the merino weight over all is warmer.
Currently I have the impression, that winter in Germany is over, 15*C in Colone???
Let's discuss swimming breefs, please!