Rescuing a Varnishing disaster?

[LostInSwiss]

Hi all. I am hoping someone can advise on how I can improve my disaster.

I have a log cabin with a varnished sloping pine tongue and groove (horizontal to the slope) ceiling.
In one of the rooms I replaced half of the ceiling with new t&g due to having to do some roofing repairs.
I varnished the new wood with x3 coats of ronseal varnish clear polyurethane satin. I was hoping this would darken to the existing wood (honey/yellow) but it was way out, perhaps it would match in 20 years but not now.

I then totally messed things up as follows:
I varnished over the ceiling again with ronseal varnish antique pine polyurethane gloss (I did not realize I had bought gloss until the next morning..). The antique pine was way too thick (like treacle) and went on very patchy over the existing clear, so I thinned it down with some white sprit which on the sloping ceiling slowly pooled on the planks. It looked awful. While still tacky I rubbed it down with an old thinner soaked towel.
Now I have a two tone ceiling and the new wood is a mottled gloss!
I know I cannot save it without starting from scratch but I don't have the time to sand it down so I am looking for things I can do to improve it. Here are my thoughts that will probably only make things worse. Please let me know if these or any others might work..

varnish over again with clear satin - would not fix the colour but would get rid of the gloss? Should it be roughed up first to promote adhesion?
varnish over again with antique pine satin - to try and fix the gloss and the colour. If I go this way how do I make it constant?
paint the whole ceiling white? Is this even possible over varnish? How?

[aeromech3]

I am no expert, hope one will be on soon, for the last option watch this u-tube and most here will recommend something like Zinsser, mind there are many products, but you have to work fast and best not have a warm room, I understand it is quite fluid so on a ceiling might drip a lot and a small roller could be useful!
https://www.youtube.com/watch?v=SJ0nJtBKULk
As said no expert, maybe some other products are more suited like Fossa Block and Bond but these might be shellac based and unsuitable for use in an enclosed area.

[dewaltdisney]

The issue is one of absorption. Polyurethane lies on the surface and although there is minimal absorption as the first coat grabs and I cannot remember, as I have not used it for years, but I thought the first coat had to be diluted? Subsequent coats bond to each other and ultraviolet light and moisture makes it yellow. The water based, more commonly used today stay clear (unless tinted) but there is no tone change.

Sadly, layer after layer of different tinted poly varnish is going to be too difficult to correct easily. My advice is to pull the boards off and reverse fit them so you have a clean surface to start over and hopefully get it right. While you are at it, paint the tongues as you fit each board so any shrinkage insitu does not show white lines. It may sound a lot of work but I doubt any amount of sanding will result in a finish you will be happy with on the existing face.

DWD

[LostInSwiss]

thanks all for your comments. I think i will try the Zinsser product. The room could do with lightening anyway. I had not thought of pulling and reversing the boards. Good idea for another time.

thanks

[arco_iris]

Not sure that the boards will reverse, t&g cladding usually has a chamfer one side of each edge.

When I tackled a similar scenario, I stained all the boards laying horizontal on trestles, including the tongues, then fitted them when well & truly dry.