Firstly, you may qualify for a grant - check with your local authority or Citizens' Advice Bureau (take note of conditions attached). Secondly, there are several different types of insulation available and the Citizens' Advice Bureau probably has a booklet on some or all of the types PLUS a list of associations of installers. Once you have decided on the type then you can find out who would be the installer nearest to you. I had foam installed a few years back (less than 5 years ago), very satisfied, the installer was from near Derby and came a long distance for my job. You can in the end compare prices, etc. - suggest you check whether WHICH? have done a report recently on something like this (e.g. ask at library, or phone Consumer Association) in order to get more food for thought. I would urge you to go forward with insulation, there cannot be too much of it and you enjoy much improved comfort levels in your home as a result. Unfortunately, buyers fail to appreciate its importance and real value so do not expect to enhance property values.