Have I got the name right?

I assume you were thinking of Lowden

I couldnt find any web sites.

If it is Lowden you want, it's here.

I want a guitar with a really big sound for unplugged rhytmic work. Or are there any other suggestions?

The ultimate "really big sound for uplugged rhythmic work" would, IMO, be a 12-fret slothead Martin Dread. D-18VS, HD-28VS (probably the ultimate ultimate), or maybe the new D-15S, if you don't want to blow the kind of bucks you need for the others.

Is it true that a black guitar will have a thinner sound than one in natural wood?

Never tried one, but there's no logical reason why it should - unless they use inferior wood for the ones they're going to color because the dye will hide the defects....

Peter.