At list, all of them were coming out at around £14k for just units and fitting. Some were a little more, some were a little less, none of them were markedly so.
Hacker (Systemat range) had, for me, the best doors, but the painted finished sucked (stained easily) and only came in one white. All their other doors were edge laminated, so they looked cheap. Only offered three interior colours and there were a few weird issues with units - couldn't do a certain width wall unit, rail options were limited and only in a square profile.
Rotpunkt were one of two who had seamless lacquered doors and they had four 'white' options for me to pick from. They also gave me 16 colours to pick from for the interiors, both straight and curved-profile rails in a multitude of colours and finishes, had the widest variety of carcass options and generally ticked all my boxes.
Schmidt had decent doors, but one white was slightly warm and one too cool - I'd have gone for the latter, but it wasn't exactly what I wanted. More interior colours than the Rotpunkt (24?) and loads of rail options and colours as well. A few issues with carcass options, but nothing overly dramatic. They were the most expensive, but started discounting almost immediately if I signed up there and then.
Mobalpa had a lovely door with a rounded profile, which ticked a lot of boxes. Slightly cooler white than I wanted, but I could have lived with it. Only a few interior colour options, same for the rail, but on a positive note they have slightly deeper base units, so you got a little more space. However, the interior finish sucked (cheap laminate, the 'bobbly' style finish) and they couldn't do me normal-height wall units with lifting doors, only two-thirds height.
Nolte had decent doors, but only one finish I could have lived with and not in a white I liked (too much blue) but suffered on carcass options and rails, etc. I'd have had to compromise a lot on my design to accommodate some of their stupidity and I didn't really feel like they were 'into' the project.
As for the ones that didn't make the final list...
Beckermann were one of the cheapest but their doors were all edge laminated, nothing as nice as the others. Interior and rail options limited, but carcasses were about the same as the others. Finish was okay on the interiors, but just okay.
Nobilia (fashion range) were pretty much the same as Rotpunkt, albeit with a slightly more limited palate to deal with.
Masterclass (an English brand) were just awful. Horrible door finishes, very limited carcass options and generally felt a bit 'second division'.
Wren were actually okay, but I wouldn't buy anything from them due to their reputation and sales tactics. Door finish was painted and very thin at that, everything else was liveable with for the price. Carcasses were thinner, fixings were cheaper, etc.