Ey up Moxxey!
Prices from the "Whathifi" reviews of the UE40B8000 and the 46" version (which I believe are the panels used in the BV10) are priced at £1390 and £1930 respectively (I quote these as I assume that Whathifi quoted the list price in the review). That's a 38% differential.
Although the screen diagonal is only 6" larger that actually equates to a 32% increase in screen area!
The B&O prices show only a 29.5% increase - Bargain!😂
You may be right about the BV7-40 (if you already have speakers) but it's like a BV7-46 would be ~ 30% more expensive!!
p.s. just had a quick, one page skim at best prices for the Samsungs - £1230 & £1630 respectively, i.e. still maintaining a 32% differential. On a secondary note, these models are in the process of being replaced by the "C" models, including 3D - the 46" model is £2199.
Although I wouldn't buy one (the 3D model), I did watch the demo reel in Currys at the weekend and I have to say it was pretty impressive as a novelty feature!😁