By Lars Mucklejohn The Bank of England has reportedly spent more than £20m on maintenance-related contracts for its Grade I-listed building since last September. Financial News reported that, based on analysis of its contract portal, the central bank had spent £7m on vents, £3.7m on pipes and £1.9m on cables for the iconic headquarters. Cleaning costs for the Bank are reportedly £1.7m per year, according to one contract, while its brass doors are said to cost almost £90,000 a year to maintain. The Bank moved to its home on Threadneedle Street in 1734, which was designed by architect George Sam…