This is a pretty good site that I refer to every now and then.
That was me.
Our house had always been cold esp on the north facing side where the bathroom and my daughter's bedroom are. Cost us £150 through our energy provider (it was £150 per product, IIRC, but I did the loft insulating myself).
A surveyor came round first and drilled a pilot hole to check the thickness of the cavity - it has to be a certain minimum or they can't do it, we were told - then the 2-man team came a few weeks later and did the job. Not a lot of mess. Took them half a day.
It has definitely been warmer in the house since we had it done. We have a few of those 'card and plastic strip' thermometers (maybe not very accurate?) - seldom do they drop below 18C. Still got our first winter to come mind!
£150 doesn't sound to bad....
Having a quick scan of Morty's link. There are 3 types of insulation. Which one did you have?
Sounds like the mineral wool variety! Here's a link that tells you what the other 2 are: http://www.cus.net/insulation/subcats/cavitywallinsulation.htmlCan't see the bit about types, but we had the stuff that looks like yellowish wadding. They fed large bales of it into a giant hopper that shredded it and blew it along a 6" hose, then injected it under pressure through nozzles into the cavity, checking to see it had reached everywhere as they went.
Cost depends on the size of your house (obviously as more material required for a mansion than a mid terrace!!)
Cost me £200 thru British Gas to have a 4 bed detached done! Get them to check your loft insulation too as you can get similar deals to increase that as well.
Had this done at our last house; well worth it. Check with the EST if any grants or reductions are available.
Typically I need a new boiler (no heating or hot water for three days now) and there are no grants available for 'rich' people.
check your wall ties before blowing any foaming agents in. In fact, check your wall ties full stop. Ian - let's have a word about this tomorrow night.