I think the most important point is to consider your house (is there a cavity wall? any moisture issues you are aware of? is it listed, and if so, why was it listed? etc.) to make the best decision. But definitely not a construction expert, so don't take my word for it.
A good place to start looking might be the Energy Saving Trust website:
Find out your wall type, costs, savings, and financial support available to you if you're looking to insulate solid walls in your home.
energysavingtrust.org.uk