*see UPDATE below* Some great fares are available based on classic European airline British Airways (with help of their partner Iberia. Cheap return flights from Europe to China. You may either consider to fly to Shanghai, Beijing or Chengu. The lowest fare is when booking round trip tickets from Spain (Madrid, Barcelona). But there are plenty of other interesting options. For still attractive fare you may depart from main airports in Italy, Belgium, Netherlands, Paris, Switzerland or Dublin. 
*UPDATE* - We have revised this deal as its still available. We are also addiong a suggestion on flights from Germany based on KLM / China Southern Airlines. Please refer to below booking samples if interested in this offer with BA.
If interested in this latest British Airways promotional sale please look for flights till 10th of December 2015 and from 4th of January till 11th of March 2016. Based on travel date of your outbound flight to China. Max stay 12 months. Book by 8th of October 2015. To check your connection possibilities you may consider service of Skyscanner. They allow to quickly find out which low-cost airline is connected from your hometown.
Before you book - some of the flights require change of the airport in London so choose properly routing of your flight! (transport costs between the airports are not part of the contract).
Booking samples - look for flights to Beijing, Shanghai or Chengdu
Germany - China from €444 (China Southern Airliens / KLM)
Dusseldorf - Beijing from €447 (Based on Cathay Pacific)
Travel dates vary by each origin. The easiest way to check lowest fare is to use service of Ebookers. (use +- 3 days searching tool).
Booking sample of cheap return flights from Europe to China from €364 here. In this case you would be departing from Barcelona to Beijing on 19th of February 2016. You would be returning from Asia back to Spain on 4th of March 2016.
