Thanks for all the info so far.
I was an 'Ashdown MAG300 EVO II' head I had before hand. It really didn't agree with me, and neither has any Ashdown stuff that i've played through. Don't get me wrong, I still think they are great amps - I've seen a wealth of bass players achieve a great sound from them. They're just not for me, far too woolly.
I'm really interested in the Warwick LWA series after hearing what you guys are saying about it. As I said, I felt the Mark Bass tone suited my setup a lot better than anything else, and if the Warwick is similar to that, it's definitely a contender. I just wish I could get my hands on one to play through, some serious thinking required. It does look stunning, which is the most important thing, right?
The LWA 1000 is incredibly tempting, extra headroom can never go a miss. Pretty sure I've broken it down to Mark Bass LM and the Warwick LWA - I've even considered ordering both, comparing them at rehearsal one night, and then sending one back. That's a bit of a mad hassle though.