Thanks everyone, good advice. A bit of trial and error learning, with a vertical learning curve...
Looks like I may go for either the Creality CR10 or the Ender 3, then have a play printing some existing items to see whats possible before I do my own designs.

Well, I didnt think this post would get so popular! but thats great, have learnt a lot just by looking suggested things up.

So, Software....

I am thinking of using sketchup as I already use this quite a bit for different projects and can find my way around it well.
Has anyone else used it and think there is better? Preferably free or open source...

What's everyone's preference?

All great advice everyone, thanks for the input!

Update -:
Stop the bus, just found a solution!
For anyone else searching I changed this in the sitemap

Text item=LastUpdate01 label="Last seen [%1$tA, %1$td/%1$tm/%1$tY %1$tH:%1$tM]" icon="network"

Works perfect now!

Hi Everyone,
I am having trouble getting 'Lastupdate' to work.

I have included

DateTime LastUpdate01 "Last Update"     { channel="mysensors:multimeter:gateway:multimeter_3_3:lastupdate" }

in my items file.

I am seeing this in Openhab Log

2019-06-11 19:28:46.275 [vent.ItemStateChangedEvent] - LastUpdate01 changed from 2019-06-11T19:12:52.000+1200 to 2019-06-11T19:28:46.000+1200

Added this to my sitemap

Text item=LastUpdate01 label="Last seen" icon="network"

But no data is being displayed in my sitemap?
What have I done wrong this time??
Thanks for any advice.

@fredswed Hi, did you ever get this sorted out? I am facing the same issue and cant find out whats going on.

Thanks for the response. All good points that I will investigate. I am happy with the engineering (avionics Eng by trade) etc
At the moment I am looking at the Ender 3 pro but still researching.
Cheers

Ok I am thinking of getting a 3d printer but do not know where to start and what to stay clear of!
What's everyone using in the way of printer and software?
Any advice greatly appreciated!

@bgunnarb thanks for the reply. That’s what I thought, that the battery monitor is included in the library. I just don’t know how that part gets the info through to openHAB. I am using the Ethernet gateway by the way. I have managed to get the info through using the multimeter function but I think there is a better way for battery level!

@dbemowsk Hi, Thanks for the reply. I am very new to Mysensors and not a programmer. I think the sendbatteryLevel is part of the included libraries but not fully sure. I am seeing both voltage and percent in the serial monitor but just cant work out how to send it through the gateway to the controller (openhab). I just cant work out what extra I need in the sketch to do this?