That is a very good question, because not everyone wants to build their own watch or invest in a nicely kitted out workbench to accomplish the task. Fact is, some Bergeon tools, case press, blower, head loupe, cleaning ether, screwdrivers, vice, clamps, tweezers, polishing cloths etc can easily add up to over £1000 worth. Yes, you can cheap out, but guess what, those tools will soon scratch your watches.
So here is a short list of some handy builders, who can sort the dream dive watch job out for you.
Tempus offer custom buolds, mainly Seiko dive watches naturally, but they do some Casio stuff too. They also do repairs, like re-lumes, polishing, custom casebacks etc. So you can refurb something that you inherited maybe.
They are UK based by the way.
Cheshire based Seikomods really have the off-the-shelf concept sorted. You can mix n match cases, bezels and dials to your hearts content. Then they ship it out. But wait, they are about to launch a Configurator, which will let customers choose from a wish list and then have Seikomods build it in-house.
Some lovely SKX and SNK Mods on this site. We love the 37mm SNK model, (see above) with its orange hand and clean black dial. No prices that we could see, but you can enquire via email.
The 42mm Explorer, with its clean dial is another winner for us.