My premium quote goes up at least 20% each year... but I still am paying the same for the last 3 years... Just ring around a few companies, get a quote from them... if anything cheaper, then go back to your original insurance company & ask them to match it... just make sure you are getting like for like regarding your policy...
Asking why the increase? Assuming you have had no claim(s) since your renewal last year, they'll put it down to the increase in payouts last year due to poor weather last year / start of this year & thus large amount of claims put in.
I always get competitive quote from O'Leary's insurance broker & AA Ireland... I've been with either of them for the last 5 / 6 years... always at least €60 cheaper than most of the insurance companies... don't be surprised when you ring around to get completely mad quotes from some of them...