UK taxation of 529 plan

Dear all:
I am a US citizen who moved to UK 7 years ago, in 2013 (so a UK resident, but non-dom).
I am the owner of the 529 plan established long ago - all payments in it were made well before I moved to UK. It is not very large (less then 100K), and 2/3 of it is basis (the amount which was put in it) which leaves around 30K grows from dividends/capital gains.
I am trying to figure out how UK treats 529 for tax purposes.

So far, I assumed that 529 is a gift to the child, so there are no taxes until we take money out from it, and then the corresponding child is responsible to pay taxes on earnings (which will be zero or near, since the child has no other income).
But I am starting to have doubts now. I see three other alternatives:
1) It can be treated as a protected foreign trust, where I am trustee, and child (or children, if we change the child name in 529) is beneficiary. Then my understanding is that I do not pay taxes, but child pays them from distribution (i.e. when tuition fees are paid), in they are UK residents at the time.
Not sure though how to calculate taxable amount here. Would it be the same as earnings in US? Or should I use as a reference point the total amount on the day we moved to UK? Or?
There are dividends (reinvested) + some capital gains/losses until 2017 ( it became fully protected)
There is also apparently some issue of Inheritance tax each 10 years for trusts - not sure what to do about that.
2) It can be treated as my investment account abroad. Then I assume I am to pay taxes on dividends every year (but £2000 is non-taxable, and additionally another 2000 can be claimed on remittance).
Next, if I take a distribution to pay tuition fees, capital gains are due (I assume all of them, from the beginning of 529 existence). But is it no me or on child?
3)  It can be treated as child's investment account abroad. Then I guess the child has to pay tax on dividends every year and capital gain tax when the distribution is taken. And if the name of the child is changed then the new child becomes responsible for taxes. In particular, if the child currently named as beneficiary in not UK resident, then no taxes are due.

Did anyone have this issue? how do you approach it?

My understanding is that HMRC view this as a settlement; in your case a settlor interested settlement. As a UK resident settlement, the trust income (if any) would be taxable on the arising basis.

Assuming the plan is not invested in UK reporting funds, future gains would be subject to UK income tax, rather than capital gains tax.

Hm..  Thank you!
From my internet search it seems there are a lot of conflicting opinions, and I did not find a clear reference to HMRC position.

I do not have a good understanding of trusts (and on if investment taxation in general). But, if it is a trust:
1) Since I am non-dom, is not it that it can be treated as protected trust, and then dividends are not taxed and only distributions are? (Or am I messing up here)?
The only "new" money in was reinvested dividends.
Also, are distributions taxed on me or on beneficiary? And if they are taxed on income, what is considered income?
2) If there is any tax on arising basIs, it is on dividends only, right? So if in a given year 529 earned less then £2000 dividends, than there is no tax whatsoever, right? (I do not have any other dividends)
3) If I change "owner" to US person now (my 529 allows change of owner), HMRC would not tax it, on dividends, even if beneficiary is UK resident, right?
What happens then, when there is distribution? Because if it is on child, he should be taxed, if it is on owmer, there are no UK tax consequences...

OK, I did some reading about trusts - and that sounds abysmal. However, these people (frankhirth - tax form for US/UK taxes):
https://www.frankhirth.com/news/understanding-the-tax-benefits-of-529-plans
say that 529 can be treated as a standard investment account, owned by the owner of the plan.

If I take this position then:
1) I have to pay tax on dividends every year, but only if the total amount of dividends is more then £ 2000   
(and in my case it was always less, so I do not have to declare or pay anything)
2) If I take a distribution I pay tax on capital gains only (dividends are taxed already), and I calculate gain from the basis on the day I became UK resident. Am I correct?
3) Next, it looks like I am taxed on those gains at the normal income rate (not at dividends rate), since those are not UK reporting assets (or whatever it is called).
It looks like saving income though. So am I entitled to personal saving allowance? (£ 500 for higher tax rate)
I made a couple of small distributions in last 7 years, but calculated as above gain component was below £ 500 both times.
4) Finally, it seems that if I now change the owner to a friend in US then I will not be responsible for taxes on future dividends or on gains in distributions.

So if my interpretation is viable, I did not have to pay any UK tax and I am clean..
Any opinion?