They look pretty similar to the ones I got today, mine are domino 5 pin but I'll only be using four. They aren't locking either like the ones in your link but are a pretty good fit and connection. I've gone for 4 plugs and sockets at the moment as you've suggested to keep the limits etc on a separate plug. Next question is what cable to use? I had some instrument cable that has four cores and is screened but my mind played tricks on me as I thought they had about 1mm core but alas it's only about 0.2 mm So not much good for 5 amps. The motor peak current is 4.2 A so I'm expecting anything above about 1 mm would be sufficient and not give me too much volt drop over the 4 to 5 meter run (preferably screened). how important do you think the screening is? The most crucial part of the screening I would have thought is in the step pulses to the driver as any parasitic elements on this line could distort the wave form but these are a good distance from any motors (noise sources) and very short so I'm not expecting problems there.

I had thought of using Cat5 cable and doubling up the cores (as it 8 core) This would have made a neat solution as I can get them ready made in different colors from ebuyer pretty cheaply so could put RJ45 type sockets (which I've already got from an old 20 way router box) on the back of my control box and on the enclosure for each of the motors keeping everything neat and tidy and no chances of noise being a problem. The only applications I've seen using POE (power over Ethernet) go up to about 720mA per core so I'd only get 1.5A on a pair of cores which isn't enough.

I screen everything, maybe a bit daft but I never get problems with noise. Well thats not strictly true as on the lathe and the mill I am doing most of the control stuff (limits included) are 24v and some of that I dont have  screened. I always screen any 5v stuff and all motor and encoder lines are screened. SY cable is good for the motors and eBay usually has a fair bit in the 1mm and under.
Hood

hmmm I suppose trailer / Caravan cable would do but it's not screened and not particularly cheap.

I'll do a search for SY cable thanks....

Not much on ebay at the moment but it was something I'd forgotten about I'm more used to calling it multiflex or metaflex I think as the sparkies used to call it when I was a mere lad in the apprenticeship. I've got a bit of time yet to ge the cable I'll use anything for now just to get stuff working. I'm still waiting for AFC or BSL to get back to me about the pulleys. I'll harass them again tomorrow. I'm on nights at the moment so sorta run out of enthusiasm by the time I get home and the shops are open.

Your limits go straight to a contactor do they ? So it knocks the juice off if they hit?

No my limits go to a relay board that I made up, this allows me to use 24V to the limits and just have a short shielded 5v signal wire to the BOB see pic below of the board I made.
Hood
ps thats it just getting tested after soldering so all the link wires would be replaced by switch wires.

Did you mill that PCB or etch it ? I had a bad experience with Ferric Chloride once in my youth making PCB's on a hot sweaty day and ended up with the stuff all over my face..no lasting damage that you can see but was pretty unpleasant for a few years.  Nice to see the ol LED's there multi state LED's would give you red for hit and green for good. The saga continues with the pulleys. I emailed them (BSL) on Saturday to ensure they didn't try and match like for like with HPC but alas it did no good. I phoned them this morn as I hadn't heard anything and they hadn't progressed it at all stating they items didn't look standard. Anyway I explained it all again that as long as I had the ratios and the belts etc roughly the same width IE the system can handle the torque then I could take almost any pulleys. I was on the phone for about 20 minutes explaining I want standard items nothing fancy no matter about flanges or bosses or width of pulley etc etc as long as the 24 tooth and the 72 tooth and the belt matched then it would be ok. I did admit that in my ignorance I had completely misled them by giving them the spec form HPc and asking for a price so it's not really their fault. Anyway you live and learn and have great hopes for tomorrow. I had a good buy on eBay last night got a ER32 R8 collet chuck for £5.75 and a complete collet set up to 20mm for £12 so that should keep me busy for a bit. The gent that had put my lathe and mill base in his locker is in work today/tonight (at long last) so hopefully I can finish drilling and tapping that and it'll be ready for painting and fitting tomorrow.

Hood etched the PCB for his relay card and did a great job. That Hood is handy as a side pocket. 

Brett