Daughter and her husband have several different seats in their mkII Jazzs, including a rather large rotatable Recaro Zero1.
I seem to recall that Jazz wasn't listed on quite a few seats and daughter is pretty cautious about these things, but I think it's just a matter of trying them and making sure it fits OK - ie on the Recaro, that the leg reaches the floor etc, although that one is listed for Jazz.
I'm aware of the top level fixing, but have never seen a seat with it - none of ours do, and that's amongst both daughters and our own.