I'm afraid that I haven't tried black ALPS, but most people prefer the feel of Cherry MX Browns over them.
If you're interested in easily replacing keycaps, then an ANSI (US) layout makes sense, but UK ISO boards should not be too difficult for to find, at least for Filcos.
I would advise against the Ducky 1087, but Leopold and Filco are both good choices. The Filco is generally regarded as higher quality, and it should not be too much more expensive if you're in the UK, since you would probably need to import a Leopold. The big difference between Filcos and Leopolds are the stabilizers they use for the larger (backspace and wider) keys. The Filcos use Costar stabilizers that make pressing the large keys feel fairly close to pressing the small keys, but can make it a little obnoxious to remove the keycaps. The Leopolds use Cherry stabilizers that enable easy removal of the keycaps, but also make the keys feel a little mushy. If you're looking for a board with Cherry MX brown switches, then I'd advise going with the Filco.
www.keyboardco.co.uk is the official Filco distributor for the UK, so you should see if they have anything that looks good to you.