Noisekiller UK tells me that Lead-lined engine blankets are available for the engine and bell houing areas. They cost £78.26 and £91.30 each, plus carriage.

These would be for my Defender 110 CSW Td5. I wonder if any of you have used them, or a similar thing. I've already fitted Noisekiller's standard kit and unless these blankets are super-good, I'm somewhat reluctant to spend more money and have the items shipped overseas at great expense.

Do a search someone posted a link to the company that supplies noise killer and you can get the bits for a lot less than noise lets make a killing are charging

These are speciallialy made blankets like an engine tea cozy that fit over the top of the engine. I was told repeatedly by noisekiller that these are the best things to fit as they stop the noise at source. Given that nearly all the noise from the TD5 comes from the top of the engine it makes sense.
An alternative approach is to fit decent sound proofing material across the whole of the bottom of the bonnet. My old E300 merc has a massive blanket fitted under the bonnet, get one of these from a scrap yard, it could save you a fortune.