two friends of mine did it in 10 hours. I agree, they both had 2500+ hours and an FAA ATP.
I think that your best change is to do it as soon after your initial FAA IR or after 500+ of instrument flying later. That's when your are the most proficient.
It's hard to say. The standards are higher than the FAA in few spots : ILS deviation is only 1/2 scale instead of 3/4 scale and Minimum descent altitudes are +50 feet - 0 feet instead of +100 feet - 0 feet. En-route altitude hold is +100 - -100 feet like the FAA. You also do single-engine holds that you don't do for the FAA but the FAA is more difficult with the Partial Panel Approches that you don't do with the CAA.
Also,
Don't forget that people in Europe get their IR with 40 hours of training equivalent to the FAA. Also, these peoples have ~180 hours TT when they start their initial training, so far from being gods ... sorry for those who think that they ARE god ...
good luck.
PS : I'll let you know after I finish my conversion ...