I am researching external insulation for solid walls (that part of my house has).
The Energy Saving trust has a leaflet of advice (but from 13/06/2006): Practical refurbishment of solid-walled houses (CE184)

Here is a useful summary: http://oxfordsolar.energyprojects.net/links/tech_solidwall.htm

One firm that I may get a quotation from is: Westville Insulation

As it will be costly I am not rushing but trying to get as much information and understanding as possible before going ahead. I think there may be grants for this soon.

Although the house is detached, because of other extensions and abutments the solid wall area that needs covering on four sides totals about 90 m2. The typical temperature difference between the two sides of the wall measured with an IR thermometer is about 10 C, which leads to a power loss of about 2 KW through the walls. There is also about 18 m2 of double glazing in this area. As the different family members have different circadian rhythms the heating may be on for 18 hours a day, so as well as comfort in the solid wall areas there will be significant cost & emissions savings.