I advise on energy saving measures and have completed the MSc sustainable Architecture course at CAT. I am a member of TTLewes energy group and am involved in Lewes Eco Open Houses and Brighton Eco Open Houses.
Internal solid wall insulation can be easier than you think. I have successfully installed high performance laminated board in my 18th century house.
Acrylic secondary double glazing is cheap, effective and near invisible.
Swapping halogen downlighters for LED, plus using CFLs is hugely effective in reducing footprint and very cost effective.