Is there a reason why you don't want to use the direct flights to Gdansk/Danzig from places like STN and LTN?

Perhaps you could also put some dates in, it will vary by time of year. Air Berlin goes there from Berlin in the Summer, but it's only one flight or less a day. It used to be a BA codeshare, not sure if it still is. There is also a Finnair service from HEL.