LONDON, Jan 17 (Reuters) - Shopper numbers across Britain rose 1.5% in the week to Jan. 15 versus the previous week, driven by a return to high streets, researcher Springboard said on Monday. It said shopper numbers, or footfall, last week were up 7.2% on high streets week-on-week, though down 4.9% in retail parks and down 4% in shopping centres. "It seems that whilst the government"s (COVID-19) Plan B guidance to work from home if possible is still in place, there are the first signs that employees are starting to drift back to the office," Springboard director Diane Wehrle said. The researcher said overall footfall was 21.3% lower than the same week in 2019, before the coronavirus pandemic impacted traffic.