Some valid points from Jan there.
Airfield / Airport / Aerodrome are matters of local terminology, he's right, we're more likely to call GA fields "airfields" than airports, but equally nobody's likely to get precious about it.
Indeed, height in feet, visibility in metres, wind in knots (but on the continent, m/s isn't unusual), altimeter setting (QNH, but also we often use QFE) in hPa - NOT inches, runway length usually in metres, fuel usually in litres, temperatures in Celcius - and indeed PPR for the vast majority of airfields. In the UK we have a couple of popular commercial airfield guides: "AFE" and "Pooleys", and it's pretty much essential to have one or the other, which contain all this information and actually both are much better than the standard FAA airport guides.
The concept of "differences training" is common in the UK and Europe, and pretty easy to grasp. Basically the licence gives you single engine, fixed nosegear, normally aspirated, fixed pitch prop aeroplanes for day/VFR. Everything else is an add-on. However, all this means is that for any difference from that, you need training as required and an instructor's signature in your logbook once only. It's pretty much a commonsense requirement anyhow, as in the USA you'd generally do the same, just the signature isn't necessarily required. Clearly any decent instructor will take account of your prior experience and not require any more training than you actually need.
Personally I manage serious IFR flying quite happily in a PA28 with some reasonable avionics, as the distances in the UK and northern Europe, along with lack of too many high mountains don't really make something meatier all that necessary. In winter you may not want to go IFR at-all on the other hand, due to icing risk, unless you have something rather more expensive - but plenty of parts of the USA are like that too.
G