Reports last year attributed the delays to design changes as well as bad weather and the small site itself, which made it difficult for the team to get material on site and move plant.
A Jarvis spokesperson said staff were due to move into the office next week. He added that the scheme was delayed by a month to allow archaeological work to go ahead.
The spokesperson said: "We always said we would move in in the second quarter of 2004. People are moving into the building within the timescale envisaged."