I'm going there on Tuesday and will be back next Monday with more tips
Lemme check the LOT site!!! The prices on opodo.co.uk were anything between £100 and £200!!!
EDIT: The PLN 259 price is the special 2-week APEX fare. Non adv-purch fares are a LOT (no pun intended) more expensive.
Further update: Train takes about 4 hours and costs around PLN 110 in first and PLN 75 in second (one way). BTW the real difference between second and first if my 2 KRK-WAW experiences are anything to go by is that first isn't crowded.
for further train info
www.intercity.com.pl