Firstly the Alliance insurance has nothing to do with your mortgage issues with PTSB.
It seems you are underinsured. What is the reinstatment value of your home, this is not the price your house would sell for, it is the amount it would cost to rebuild it. Do you know this.
I do not understand you sayiing the period has gone up by 400 € when it has gone from 200 to 360, an increase of 160 annually?
It has become normal for insurances to up the premiums to take account of increased building costs. Normally you can object to this if you think they are wrong.
How much is the buildings insurance is for contents - have a look at your policy. Sometimes you can reduce that cover and it brings the premium down.