By Sinéad Carew and Alun John NEW YORK/LONDON (Reuters) – After tumbling earlier, sterling rallied against the dollar on Wednesday following the Bank of England’s (BOE) purchase of UK government bonds, letting some air out of the greenback’s progress broadly after it had touched a fresh 20-year high. The BoE said it received 2.587 billion pounds’ ($2.78 billion) worth of offers in its first bond buyback operation aimed at stabilizing the market, and had accepted only 1.025 billion pounds’ worth. The central bank had committed to buying as many long-dated government bonds, know as gilts, as nee…