The FTSE 100 .FTSE was down 0.2 percent by 0859 GMT, as a pull-back in oil and tobacco stocks, which had pushed up the index in the previous session, more than offset gains in banks and materials.
Economists polled by Reuters all expect the BoE, which raised rates last month, to vote 9-0 to leave them at 0.75 percent. Most do not predict a further rate rise until after Britain leaves the European Union in March 2019.
“Following August’s hike it is likely to be a completely forgettable get-together, with it being hard to see the newly re-signed Mark Carney and his colleagues doing anything to shake the markets,” Connor Campbell, analyst at Spreadex, said.
Sterling, holding steady near one-month highs, also weighed on shares in big international exporters, which are heavily represented on the index.
Marks & Spencer (MKS.L) was the leading loser on the FTSE, down 2.6 percent, while Morrisons fell 1 percent despite its first-half profit growth beating forecasts and a quarterly sales performance that was its best in nine years.
Some analysts were concerned about pressure from low-cost competitors, arguing the strong update was a one-off.
“The question now is where can Morrisons go from here? There remains some intense pressure from discounters, whilst Tesco has lately announced its own discount chain aimed at countering the German upstarts. Further pressure on margins seems inevitable,” said Neil Wilson, analyst at Markets.com.
Other retailers were also under pressure on a negative read-across from poor results from the country’s biggest department store group John Lewis, whose profit was wiped out in the first half as it was forced to match discounting by its struggling rivals on a fiercely competitive high street.
Ocado (OCDO.L), which rose 2 percent, was an exception.
Banks provided some support to the FTSE, with shares in Royal Bank of Scotland (RBS.L) up 1.5 percent as its chairman was reported as saying the lender could pay a special dividend. HSBC (HSBA.L) and Barclays (BARC.L) also rose.
Miners were also in demand as copper prices rallied after a U.S. official said Washington had invited Beijing to restart talks aimed at resolving their trade dispute.