The building - equivalent to 16 Premier League football pitches - is one of the largest distribution facilities in the UK.
The depot will initially service 50 stores, ramping up to 250 stores over the first half of this year.
But B&M was quick to point it's still business as usual, despite the sale.
A spokesperson said: “B&M has now committed to a 20-year lease at this facility and are currently recruiting for a wide range of roles.”