What did you think to it?

Dialect and perfectly acceptable.

Sounds OK to me, though I'm not sure if I have always used it or if I have picked it up from my husband. We are both from Yorkshire.

I think it may be a regional variation.

It’s common here in the NE, too.

I do hate misplaced or misused prepositions, ‘different to’, ‘forbidden from’, ‘bored of’, ‘’inside of’ etc. but I don’t think they will ever revert to being correctly used now.

It's regional, mainly Yorkshire.
Nowt wrong with that!

And less and fewer but I won't start now.

Usage varies by time and place and as long as the meaning is clear, I tend not to mind.
But I do mind about lay and lie.
Lie is an intransitive verb, ie it doesn't take a direct object. Its past tense form is lay. I lie down, he lay down.
Lay is a transitive verb which needs a direct object. I lay the table. He laid the table. The hen laid an egg.
Formerly, there was the reflexive usage. She lays herself to sleep. He laid himself on the ground.

The more I m thinking about it the more I think I use both

Both.
As well as, What do you think about it?

I haven’t heard anyone say it but it sounds sensible enough.

Witzend

I keep seeing this, and have just seen it yet again!

Is it me, or isn’t ’What did you think of it?’ far better?

Both are correct. Your example is from colloquial English. Found more in the north than south.

Definitely ‘What did you think to it’ for me

I am often surprised at how many people use different prepositions to the ones I am used to. People become bored of, they say less than rather than fewer than and due to and not owing to. All things that I was taught were wrong at school over sixty years ago but who is to say they are still wrong.

One thing I can't get my head round is the fact that I would say "I am going to lie down." Whereas a lot of people say "I am going to lay down." Which is correct? Isn't one transitive and the other intransitive?

I would say of, but the other way is just another way. It may be just a fad or something imported from elsewhere in the Anglosphere, or from people whose first language isn't English. So long as meaning is clear I don't think it matters all that much.

People also say say 'different to' instead of different from. I think Americans often say different than.