It looks like there are two or three VE Bus to USB interfaces that are needed to programme the Multiplus II
ONE the Victron VE.Direct to USB interface cable which looks like it has everything to connect to a PC and the Cerbo
AND
Interface MK3-USB (VE Bus to USB) BUT that one and the MK2 version seem to be missing a cable to connect to the Cerbo
ALSO the first one is around the £25 mark BUT the MK2 and the MK3 versions are more than twice the price 
HELP PLEASE
Only a mk3 usb is needed. Though if you don’t need to do parallel or multiphase, you can also push a config remotely via VRM.
For a MultiPlus you need the MK3 interface (the MK2 is the older/slower version of the MK3).
If you have a GX device and an internet connection you can do it over the VRM portal.
The VE.direct interface is for devices with VE.direct port.
I will have a CERBO GX
I am being told that I can use a tablet computer in place of a GX touch device, in that case can I use that to programme the MP2 and should this just be a WiFi connection or hard-wired? If hard-wired, is that just using an Ethernet Cat 5 Cable??
You really need to do some of that free online video training. It will fill all these basic gaps for you.
It is much cheaper to avoid mistakes by spending a few hours watching Guy’s excellent videos.
Watch a few vids on the topic and/or read the Remote VEConfigure manual, but you can program over WiFi.
I update my RV out in the barn from my development bench in the house over WiFi with a Cerbo & computer using the remote configure at the bottom of the VRM device list and VEConfigure3. It’s not fast or intuitive, but it works well. Basically you download a config file from the inverter, modify it in VEC3, then push the file back to the inverter.
Save your old file before you start changing.
link again please and for sure I HATE reinventing the wheel
thanks
Link to all your victron learning needs, register for free / log in - https://professional.victronenergy.com
thanks