Ken Griffin and Jamie Dimon have said they might reconsider building projects. Getty Images Jamie Dimon warned that higher UK bank taxes could affect plans for his London headquarters. The bank announced plans for the 3-million-square-foot, multibillion-dollar building in the fall. Ken Griffin has said he's reconsidering a Midtown office expansion amid a tax spat with Mamdani. London's skyline might not get the JPMorgan treatment. JPMorgan CEO Jamie Dimon said that increasing taxes on banks in the UK could thwart his plan for a new, multibillion-dollar London headquarters — the latest financial CEO to link major office investments to tax fights. When asked in an interview with Bloomberg whether JPMorgan would reconsider plans for a new London office amid calls for UK Prime Minister Keir Starmer to resign, Dimon said political instability alone wouldn't alter the bank's plans — though that could change if the UK became "hostile" to banks.…