By William Schomberg and Alistair Smout LONDON (Reuters) – British finance minister Rishi Sunak, preparing for a budget update this week, said on Sunday he would help where he could with a cost-of-living squeeze but warned that the Ukraine crisis and sanctions on Russia would add to the economy’s problems. Britain and its allies have imposed sanctions on Russia and energy prices have jumped following the invasion of Ukraine, intensifying a surge in inflation. Asked by BBC television if he planned to step in and help households with their energy bills, Sunak said: “Of course I am and people can…