From Digital Spy:
In a not-at-all surprising turn of events, the Beeb has been caught re-using set locations in two of its most popular dramas, 'Luther' and 'Silent Witness'.
According to those tweets, the building was a cereal factory in 'Silent Witness' and basically abandoned in 'Luther'. And on the Toobworld timeline, both events happened around the same time.
So they can't be the same building.
Luckily I have a different splainin, one which I've used for the repeated use of buildings in American TV shows.
Both warehouses were built by the same architect. And he used the same blueprints over again to spare him agita from their respective companies who wanted to save time and money in their construction costs.
That's my splainin anyway.....