B2B in Poland for a British citizen (Kraków)

Hello,
I am Polish/British. Spent last 20 years in UK. The times has changed and now I have a great opportunity to work for Krakow full time. This work will be remote so I don't know exactly how much time I will spend physically in Krakow. Some time here some time in Asia, some time in UK.
I was planning to set up a self-employed b2b company in Poland.
I've done a lot of reading about double taxation treaties and tax residency but it is still not clear to me. I reached out to experts who are busy and will be back to me 'in some time'. So asking here.

Has anyone been in similar situation? Note that:
This is not working remotely for UK based company.
This is not getting payed by a foreign client to your British self-employed company.

If so I assume you have paid polish tax (likely lump sum 12%) and some national contribution costs (say 2k pln).
Have you reported this as 'foreign tax' to HMRC ? And if so have you reported this as total before tax and before 'national health contribution' or you treated the latter as 'cost' therefore the 'income' reported to HMRC gets reduced by this amount.
I think I know how to avoid double taxation legally, I don't know how to avoid double national health contributions. For example if I report my full income before deductions I would be taxed on my national health contribution which sounds insane.

The other option is to get the certificate from HMRC confirming that I pay my national contribution there in UK to get a relief in Poland but this seems crazy messy. Any help please and cheers in advance. At this point it is even not about tax optimisation but rather convenience.

Alternatively any expert recommendations would be great!
Cheers!