By Laura McGuire Abandonedproperty deals have driven investment volumes in the London office market down in the first quarter of the year, but green shoots are starting to emerge. At the start of the year two major property deals worth a combined total of £436m went kaput as sellers possibly looked to refinance in anticipation of a price recovery as interest rates fall later. Plans to sell a 12-storey office block in Canary Wharf ended last month after its owners decided to withdraw the building from the market. 5 Churchill Place, a former office for investment bank Bear Stearns, was placed in…