I can't speak for those bib-tights you link to, but
Decathlon do about three grades of winter bib-tights, I think. My mate's got the most expensive ones with the thick wind windstopper panels on the front, thighs and knees, and he thinks they're very good.
For the higher end stuff, Decathlon are no cheaper than other brands, though. I have some Pearl Izumi bib-tights (without a chamois) which don't have windstopper panels, but are still extremely warm. I paid the equivalent of about 45 quid in a sale.