There are a few sub £10pp return flights from Newcastle to Poland (Wroclaw) which I've used to put to together this cheap city break 8-11th December.
Whilst Wroclaw may not be your first choice in Poland, it does have some good Christmas markets and it allows you to be able to travel cheaply, for example the bus to Krakow is under £2pp so you could easily head over to Krakow for the day or turn this into a twin centre break and spend a night there (a bargain when you consider return flights to Krakow from Newcastle are over £100). Similarly Warsaw is just as cheap.
Wroclaw does have its attractions too, from the old town and Centennial Hall. There is also some Xmas markets in the Rynek square area too. At this price I think it's a bargain of a break.
3 nights in the Boutique Hotel £84 book at amoma.com
2 return flights book at Ryanair £19.96
*If you go on Amoma on Facebook you may be able to get a 10% code which could bring this price down to around £48pp*