UPDATE 1-UK Heysham 2-8 nuclear unit back - Nat Grid data

(Adds British Energy confirmation)

LONDON, July 13 (Reuters) - British Energy's (EDF.PA) Heysham 2-8 nuclear reactor was back in operation after an unplanned closure since June 25, data from the National Grid showed on Monday.

The data showed it was operating at 164 megawatts at 0750 GMT.

A spokeswoman from British Energy confirmed the 625-megawatt reactor in northwest England was back in service since Monday morning. The company had done maintenance work on the unit after it suffered an unplanned closure. (Reporting by Nao Nakanishi; Editing by Michael Kahn)