I also did the route of PPL then IR. I did my single engine FAA IR first, as a relatively inexperienced PPLer, and I did mine in 15 days from start to finish. I didn't have any instrument experience prior. By the way, I'm not saying it was easy!!! Certainly lots of hard work!! When back in the UK I asked for a dispensation from the CAA and, back then, somehow I managed to convince them to let me do the UK multi IR in "as many hours as instructor deems necessary". Which meant around 8 hours training and then the test. Doing it this way, even with flights and accommodation included, was still way cheaper than doing it all in the UK. One of the biggest savings is actually on approach fees - in the UK it was around £20 an approach, if not more, and in the USA it was $0. So that makes a big difference.
Once you have your IR there isn't a lot of difference between countries, if you were taught well. After doing my FAA IR I did my CAA IR and then did a bit of flying in Europe and USA. USA is much easier from the point of view of filing a flight plan and the fact that many more places have ILS or VOR approaches rather than NDBs, and also more radar coverage.
Doing an approach in Greece still generally requires you to have your wits about you and remember your basic instrument flying!!!!