I've been browsing the Ryanair website to try to find a destination where you can get two
full days away. (i.e. where there's an early morning flight outbound and a late evening one one coming back).
One possibility would seem to be Krakow. If you can get to Stansted earlier enough, the 0610 flight on Wednesday is �29.99. (Arrives Krakow 0935). On Thursday, the return flight at 2140 costs just �0.01. (Arrives Stansted 2310). That would give you two complete days to explore the city.
Krakow Christmas Market takes place this week and next week. Source:
http://www.krakow.pl/en/kalendarium/?MODE=kali m&TYPE=show&IM_ID=1926
(Click the 'Tourism' tab for loads of information about this beautiful and historic city).
Accommodation in Krakow is cheap. For example The Wiliam Apartments have a single room available for �14.72. The Trzy Kafki Plis and Cracovia Guest Houses both charge �16.56. These were found here:
http://www.hostelworld.com
Unfortunately, you're unlikely to find any snow. The forecast is for rain showers:
http://uk.weather.com/weather/local/PLXX0012?x =18&y=10
Chris