I spotted this one at B&Q tonight and could hardly believe my eyes. This was at the Darnley Warehouse in Glasgow, I can't find it online and not sure if it's available in smaller stores.
The deal is for a pre-cut roll of mineral loft insulation for £10. These packs are unbranded in plain white plastic packaging and they had loads at the front of the store.
Each roll is is pre cut to allow for different joist spacing and has measurements of 1100mm x 4900mm x 200mm (5.4SqM).
Admittedly, everyone now qualifies for a grant to have loft insulation fitted, but even with the grant the price is usually around £200 and not exactly quickly installed (from personal experience). I think many people could get themselves sorted a lot quicker and cheaper by making use of this deal, although you will need to install it yourself!