UK similar population of Germany? Well it's in the same ball-park. UK: 60ish million. Germany: 80ish million. Though there are predictions that the populations will equalise in the next 10 years or so. Germany is worried about its low birth rate (slightly higher than Greece, but still below replacement - which is why people don't want to bail out Greece: even without tax evasion there won't be anyone to pay back in the future). Though the UK's birth rate is only booming in comparison: it's barely above replacement. If you're worried about space, apart from Germany's lack of understanding of tea and the need for milk in it, I can think of worse places to move to than the beautiful Extertal.
The UK's population is very unevenly spread. On a macro level, Scotland has areas that have the lowest population density in western Europe. On a micro level, Northern Ireland has most of its population in the greater Belfast area. There's plenty of space.