All is good now. A very big thank you for all the help.
For those that are interested, my sequence of events are as follows (really quite easy)
Opened HLS sequence.
Removed pixelplanes that weren't going to be part of new setup (new house for 2017)
Removed models/channels that weren't going to be part of new setup
Saved new setup/sequence in HLS
Exported newly saved sequence in HLS
Setup Xlights to reflect setup in HLS (with same universe/channel setup)
Open new sequence in Xlights
Choose MP3 and add timing if wanted
Click on done
Click on settings tab, sequence settings, Data Layers tab, then import
Choose previously exported file from HLS export files folder (.hlsidata)
Choose lights off at end (or not, your choice)
Allow conversion process to take place (each of mine took less than 30 seconds!!!)
Click on Done
I then clicked on Render All
Save sequence
Done!
(New setup in Xlights only had to be done once and then used for each conversion)
I was super impressed as each sequence I converted too less than 10 minutes from start to finish!
I then went and created new universes/channels in the setup tab, to reflect new models for 2017
New models were hen created in layout tab.
Opened a previously saved sequence, edit display elements, Add views and created a new view, including new models, saved.
The whole process really was that easy. I was overthinking it previously and thinking it was going to be much harder than it was.