You can't do the IMC rating anywhere except the UK - so that's an easy one!
Where to study? Where are you from? Where do you intend on flying? Every country has slight differences, different weather patterns, different procedures, different ATC phraseology... Etc...
I would recommend learning where you intend to fly most of the time, as if you did go elsewhere, you'd need to come back and do more training in your country of residence before you can rent there. Also be aware of where you are allowed to learn and convert to the licence of your country of residence.
Good luck finding somewhere!
A