If you are looking at getting a keyboard with a "standard" key layout to facilitate customization with aftermarket keycaps, Filco, WASD, Das would be my choices.  Cherry G80-3000 is another option and in some people's mind would be *the* standard keyboard, but it has the drawbacks of not being a plate mount board (although I suspect that would really only become a noticeable issue with black or clear switches) and also it uses an off center space bar switch unlike everyone else (that can be worked around with a homemade jig, and extra keycap, and some epoxy.)  I wouldn't recommend Leopold because of non-standard space bar and windowed keys, although that can be worked around.  Likewise Noppoo Choc Pro is a nice board but the space bar on that is non standard as well, although it has the advantage of being NKRO over USB and is very Filco-like in appearance and feel.  Those are the ones with which I have experience... there may be some others that would work well for you.
I know Filco and WASD offer ISO layout boards which may be important to you in the UK.  I would assume that Cherry does as well.  Not sure about the others.