Mister Geezer
There is no reason why an FI rating in the UK should take longer than any where else in the world as the course requires 30 hours flying and 125 hours ground school. Most schools offer the course over 5 weeks therefore when the weather is good you fly and when its bad you do ground school. Additionally if you do the course in winter for the cost of an extra hour you can do the night rating as well.
cheers
MJR