Very sorry if this has been highlighted already (haven't noticed it), but:
B&Q are selling loft insulation (standard size) at £3.00 a pack, i.e. £1.00 a roll.
It's scraggy looking stuff, but to my eye it definitely seems to do the job. It's labelled "for DIY only -- not for use in government sponsored top-up schemes" (or summat).
I saw it advertised in the paper a week past Saturday, *rushed* to get some Monday, they had plenty left, and a week later, yesterday, when I was in there they seemed to have had a whole new truckload delivered - hence my notifying it here.
John