However we were talking about the UK here, and as pointed out, that so many Polish migrants came to the UK was not due to the EU, but thanks to the British government.
Not only. The EU promotes the movement of people and goods within the bloc so they came on their own. What the British did was made it easier for Poles to get a job when other countries didn't have as favorable labor conditions. It's because they wanted high quality cheap labor. Far more Poles, Romanians, Lithuanians, etc came after 2004 than before.
and with Brexit will probably see a further surge of immigration.
The opposite is happening. Those currently living within Britain that aren't citizens are worried about their status. Many Poles have already left - Polish international moving companies are extremely busy moving Polish families from UK back to PL. Plus, many people from Poles and Romanians to students from India are not more weary of moving to the UK because of Brexit and fear that they'll be asked to leave soon after arriving.
Poland would not have been able to join the EU without the support of Germany,
Not true at all. Poland was one of 8 countries to join EU at the same time. Germany helped, and also invested a lot of money into Poland even as early as the 90's. However, we along with the other Baltic states, would've became part of the EU with or without much German help. To say that Germany was directly responsible for Poland's ascension into the EU and Poland wouldn't of joined the bloc without Germany is an exaggeration.
theguardian.com/uk-news/2017/may/25/surge-in-poles-leaving-uk-since-brexit-vote-fuels-net-migration-drop
thesun.co.uk/news/3068281/polands-cities-are-thriving-again-as-thousands-return-home-since-brexit-after-we-found-deserted-streets-four-years-ago
Their policy then also gives the lie to the fiction that the Merkeljugend migrants will ever be anything but a welfare drain because all most could ever be is cheap labor (provided you could force them into jobs...
A lot of them don't want to work. Walk through Tower Hamlets in the middle of the afternoon on a Monday or other business day and you'll see tons of guys and black clad ninjas walking about aimlessly, chatting and shopping at the stalls, pushing 2 child strollers followed by a few more slightly older kids who can already walk, and loitering about. Its clear they are in no rush to get back to any sort of job. Its the same in Germany with the recent migrants. They sit at their camps all day or walk around on the streets and complain that the internet is slow. When the governments are paying more money to the migrants than they'd ever make back home of course they won't want to get off of it. Even if you gave them a low skill low pay job that's a tad higher than the benefits they'd still rather chose the benefits since they can do whatever they want during the day. This is why citizens of so many countries are furious. There have been many reports of even old people being forced to leave their apartments because the government bought it out and is turning it into migrant housing - especially in Germany. The Swedish government is hosting migrants on a freakin cruise ship that the tax payers are paying to lease out. The Germans bought a 4 star hotel to house migrants and promptly fired all the hotel workers at a moment's notice. They don't pay for sh!t and have no plans to work. If they cut their welfare payments they'd all either get a job or leave.
There divide between the countries east of Germany and those west of Germany is deepening everyday. If Germany, Brussels, etc wants to fix the EU and not have it collapse, they need to give the states more sovereignty in their home affairs and not meddle in their local affairs. This is why Austria, Poland, Hungary, Czechy, Slovakia, Bulgaria, are saying no more. They don't want to leave the EU, but they're not going to allow Brussels to tell them what to do and what not to do within their sovereign borders. Poles view the EU as a promotion of European economies, promotion of trade within the bloc, ability to immigrate to a wealthier EU country, and so on.