Hmmm. Well first I'd like to point out (again) that I can only comment on the Home Studio Monitor and would hate to unfairly prejudice against other models in the range. And my opinion is based entirely on MY ears, and you might not share my opinion if you had a chance to listen yourself. However, in all honesty, I have to say that £500 (plus VAT) would probably be better spent elsewhere - there are tighter, more exciting, and prettier speakers to be had.
But before you go away dejected, I have a few (more) thoughts. Volt and Scanspeak are highly respected and I'm surprised the 'Monitors don't sound better. There might be an issue with cabinet tuning - the supplied port was too small for the hole and had to be bodged to fit - and a tweak of port length/diameter might help. As might changing the cabinet damping (my recollection is five years old now and I can't remember exactly what's inside). Wilmslow might be using a generic crossover - a purpose made design would be much better. And, finally, looking at Volt's website they recommend two cabinet sizes - a 30 litre, like the Wilmslows, and an 18 litre. Obviously the smaller box looses out on bass reach (-3dB at 50Hz, as opposed to 39Hz), but might sound much tighter.
In fact I've just put the BM220 into WinISD (a free loudspeaker box design program) and it suggests 20 litres for a -3dB cutoff at 46Hz, so I can't help but think the large box is a compromise - loosing bass grip for pure depth.
I'm waffling again and this probably isn't helping you, so I'll defer to my first answer - that unless you're a DIY nut or compulsive hi-fi tweaker, you're probably better off spending your money elsewhere. Of course, if you're anywhere near Leicester you might be able to arrange a demo at Wilmslow Audio, or if you're anywhere near Cambridge/Peterborough you could come and hear ours.