They have given us the requirements and that this will suffice
You say that that will suffice because you have in writing a statement from the office in Szczecin that it will be OK? Or because your reading of their information says that? If it's the latter, I really urge you to remove that potential problem. Once you have paid for the reception etc (you'll need to pay at least a good chunk of it up-front), you really are stuffed if the office won't accept your paperwork.
In your position I'd be getting a sample from the office in the UK that issue the certificate, having that translated and sending it to the Szczecin and asking them for written confirmation that that particular certificate will be accepted.
My register office wanted an official copy of my birth certificate, translated by a sworn translator
I once had a residency permit application rejected because the sworn translation of my birth certificate which I provided to them was more than six months old. I tried to point out to them that my birth certificate hadn't changed since I was born and they could easily check that by simply looking at the copies and sworn translations they had in their file from my previous applications, but they insisted I had to get a new translation made.