HELP!!!

We are thinking of getting our Bungalow insulated, although we have heard some horror stories.

Whats the best way to go about it?

Our Bungalow was built in 1929 and the mortar seems quite crumbly in places? It's not unusual for bungalows of this style, I think its some kind of Limewater stuff, but I don't really know. Someone did say that when they had their property done, it blew the plaster off inside.

Should we be worried?

Also, what does it cost?

Any help would be appreciated.