I didn't see anything in the manual about wiring up in series. I'll have another look tho because I often do miss things!

Thanks for the image Neil, however what does NPN and PNP mean?

Am I right in thinking then, that input 1 can be X home, input 2 is Y home, and input 3 is Z home. Then use input 4 for all the other limit switches in series?

Thanks everyone