Never had experience of this at all.
You are correct in knowing that you should be insured for this,in your own right. I do not know the best way to go with it and that's for sure.
I would ring the company you are with for their advice. It could be they would make you legal for as long as you are away in it. BUT you must do it one way or another. Good luck.
I added our son to ours (comfort) due to me being unable to drive for a while, it was cheaper than buying stand alone insurance and lasted for the time left on my policy. did that about 4 years ago
We lent our MH to friends for 2 weeks. It was just before our insurance renewal & we added husband as a named driver (took it back off next year). It cost nothing. If we’d added him at another time, there would have been an admin charge of £25 or so.
Can’t add my sister when she visits from NZ as she doesn’t have a UK driving license - only saying in case the OP is visiting from abroad.
Not sure that you can have two (or more) lots of insurance running concurrently on a motor vehicle (had some problem with this in past many years ago IIRC), so taking out your own insurance to drive the vehicle may not be an option, but you'd have to check current practice.
Being added as a short term named driver on existing insurance is commonplace, I've done it lots of times when going abroad in car with friends and either wanting to share driving or wanting assurance of a back up driver if I can't drive for some reason. Costs vary from company to company, sometimes an admin fee as well to make the addition, but likely the cheapest and simplest option overall.
But as said, insurance cover of some kind is essential.