Well, it's a forum for Polish people living in the UK.
It's actually an American-run forum for anybody interested in discussing Poland and Poles in the English language. That also includes any Poles (or anyone else) in the UK who want to take part however only a few UK-based Poles do; there are several fora specifically for Poles in the UK. They are however obviously in Polish.
Yoiu seem quite a keen observer. One thing I've noticed is that the nationals of any given country often behave abroad differently from at home. Also expats are not always a typical demographic; their life experiences differ hugely from those of people who haven't moved abroad. In short, it changes you.
Poland is a country of 38 million people, with vastly differing outlooks on life, social class, political views, level of education, etc. There are also regional differences, albeit not as marked as in England due to post-reunification assimilationism, wartime tragedy and post-war movement.
Some people observe that Poles are more traditional than Brits; that's a false comparison. Poland is a more rural society (around 40% of people involved directly or indirectly with agriculture) whereas the UK is more urban. Urban Poles aren't necesssarily more traditional than urban Brits, and in my experience rural Brits are if anything more traditional than rural Poles.
About your "drunken slobs" statement, it's rather subjective, however there's certainly no shortage of heavy drinking among Polish men; you'd be surprised at the amount of vodka that some local shops, especially in depressed areas, sell. One key difference is that Poland doesn't really have the traditional pub culture that Britain still has; people tend to drink at home with friends and family.
But....why the unhappy faces? Very cold exterior. No smiling. Certainly no laughing
In Poland, people are very warm and friendly with people they know and like. They don't however feel the need (this is not unique to Poland; you see this in some other cultures) to be artificially polite to people they dislike or to spend time smiling at strangers. There's quite a dichotomy in Polish life between the private and the public.
About holding doors open etc, some do, some don't. In Poland it's usual to say thank you when leaving a lift (after many years in PL I do it myself). It's less usual to speak to or even acknowledge neigbours, especially in towns and cities.
About Pakistani men? You mention warehouses etc so you're talking I assume about people from the post-2004 wave of migration who are mostly younger and poorer as well as living in in cities. People meet and date those around them. If you were talking about people who'd moved to rural Lincolnshire for agricultural work, I suspect there's a very different pool of potential dates.
What was your intention?
And what sort of reaction were you expecting?
I wondered about this too. I think he's genuinely asking and is curious about the Poles he's met in the UK.