Sorry Flyin' Squirrel, I owe you an apology- they used to be around that much but they're far less now- just found a coupe of places doing the systems for £510 inc VAT, and M&P has them for £600- looks like they're doing some serious discounting.
It looks like they might actually not be doing the slip-ons for the SV any more, or maybe places just aren't bothering to stock them as it makes no sense to try and sell a £400 slip-on (I was right on that at least, an equivalent slip on- Bandit 600, say- is £400 for road legal
)