Regrettably the Joe Brown offer has long since expired Billy.
Sorry about that - it was that price a while back and then vanished - so I thought it was back. Did sound too good to be true! Trekkit have them for £229.50, and Down Sleeping bag has it for £225.
The Rab 700 does seem to be a more standard UK winter bag anyway, so perhaps look around for those, including the OM selling thread, but Trekkit have them for £204.
Carinthia 4...? then save some of your pennies for some other kit
The Carinithia 4 is rated to a comfort level of minus 15 (although its described as a 3 season bag!), but weighs 1.9kg and costs about £223.
The Rab Ascent 900 is rated to a comfort level of minus 18, weighs 1.53kg and costs £225 (if you shop around).
Your saving very little in pennies, but you are saving over 400g in weight.
I'm not convinced that down basically becomes porriage at even the first wiff of rain - yes, synthetic is better with moisture, and thats why the military tend to go for it. But synthetic isn't waterproof, and I wouldnt want to sleep in a wet bag, full stop, even my current synthetic bag. Wayne's experience seems to be the norm for most down bag users - take care of it, use a dry bag, etc. The biggest barrier to buying a down bag is the extra cost, and for me thats been the case for a long time!