Everyone living in a home their own, siting in Council tax bands A-E (or A-D in England) is entitled to having either their loft / roof insulated, or their walls. Walls are generally better bang for your buck, especially when you are getting the work done for free, but sometimes you might want to get your loft or roof done instead.
Having moved into a house a year ago, only to realise the EPC was very inaccurate (our high D was a low E), we immediately insulated the loft. I could feel the difference, immediately. Worth the sweat and spiders. If the above criteria applies to you though, you can leave the cobwebs to the the professionals.