For Europe generally - and the UK in particular, where the seas around it act as a natural temperature buffer - yes, it's would likely get quite a lot colder. Take a look at how the temperature average and variations in NYC at ~41 degrees north compare to London which is more like 51 degrees but bathed in the gulf stream (caveats involved, both coastal northern hemisphere east coast cities but a lot more land to the west of NY than for London).
Yeah that’s kind of interesting actually. All other things equal, Europe getting colder than it has been in the last few hundred years would be bad. But, in the context of the entire earth getting warmer, Europe getting colder than it would get otherwise does seem like a good thing.
As far as I can tell this is not expected to be a direct effect of the Gulf Stream weakening. I think the Gulf Stream just warms. The ocean carrying the Gulf Stream may also cool due to the general moderating effect of water, but the ocean itself isn’t going anywhere.
Hotter or colder Europe is a minor problem. At least we have air conditioning.
If Africa becomes uninhabitable, everyone there will either die or migrate to Europe. Most EU coutries already hope that they drown crossing the Mediterranean. It's already happening, but the migration now is very low. When the migration will increase, I see WW2 repeating: concetration camps, genocide, shoot-them-at-the-border type of things.
