First of all, as far as I remember Gdansk is connected directly only with 5 big international airports, that use traditional airlines: Munich, Frankfurt, Copenhagen, Oslo and Warsaw (which won’t help you much in this case). All the rest are those B-airports with low cost airlines (Dublin is another big airport but it is only connected with Ryanair here).

For everyone who used low-cost airlines before it is obvious they use B-airports, outside the city centers (usually about 50-100km one way). So I didn’t have to write that. But even though they are outside of city centres, they are actually well connected with those big cities, and the trip by bus or train takes usually about 1-1,5h one way. Trains are in fact the most expensive way to get to/from those airports, buses are way cheaper. And even with added costs of bus or even train, still it is much cheaper than using traditional airlines from big airports.

By taking London’s example, there is no way to get a direct flight from Heathrow to Gdansk, so it means stopovers on the way on some other big airport, which makes in fact the trip longer than with low-costs with added time for the bus/train trip. So it looks like this:
a) London Heathrow to Gdansk will last at least about 5h (including stopovers) and will cost in June min. 180-200£ (return flights)
b) London Stansted or Luton to Gdansk will last about 4h (including 1h15min bus ride from/to London city centre) and will cost in June about 80-90£ or less (return flights and also including the tickets for the bus to London’s city centre which may vary from 2-16£ for return tickets – http://www.easybus.co.uk/ , http://www.terravision.eu/ )
Moreover is Seb’s logic you can get from London city centre to Heathrow in seconds and even for free, which is not, so you have to add that cost anyway, which makes the difference even bigger.
Same goes for Stockholm to Gdansk, which will include stopovers too and will cost twice as much using traditional airlines too, and will not be faster anyway, compared to Stockholm Skavsta Airport + bus.

I admit, there is a chance you might get a cheaper ticket in some kind of promo in low cost airlines in few months from now, but it won’t be much cheaper, especially for the trip to Poland in June. Like again, with London’s example, lots of Polish students go to UK for the summer for work and those who live in London during the year go back for the summer to Poland for holidays. Airlines have been aware of that very well for years, and they have no interest of dropping the prices in those months, because they will sell those seats anyway. Simple as that.

Obviously Seb wanted to shine with his knowledge, but he didn’t do his homework well, not for the first time and not for the last. I don’t care about his overgrown ego, but I can’t let him misinform some of you about flights to Gdansk which might cost you a lot of money, that you could spend on something else, instead of traditional airlines. I used flights from/to Gdansk about 20 times or more, from/to various airports in Europe, including about 5 times to London (Luton or Standted), and experienced that myself how it works, so I think I can say a lot more than Seb about the cheapest flights to/from Gdansk. Decision is up to you.