I will second Mr Owens suggestion with the Scarpa SL active, as my friend bought a pair a few months ago.
He wanted boots to take advantage of the heavy snow in Cwm Eigiau, and to wear year round, over challenging terrain.
Their not cheap, at around £260-70 but there's no denying their quality, as their a serious four season boot, that if looked after, should give many years of sterling service.
When your buying a boot of this quality, and price, they really represent good value, as your unlikely to be needing another pair of similar 4season boots for many years.
Their Vibram sole, has a very deep tread pattern, and you only have to look at them, to see their quality.
Its such a popular boot, that i recon you may pick a pair up for a slight discount.
Visit your local Cotswold or good boot shop, and try on a pair, and if you have that kind of money to spend, they should certainly be on your final list of boots.