UK'S Big Yellow gains after activist Ancora urges strategic review, including potential sale

** British self-storage company Big Yellow Group BYG.L rises 3.9% to 830.5p, highest one-day gain since 24 June

** Activist investor Ancora, which owns more than 4% of the company, has urged Big Yellow to pursue a strategic review, including a potential sale

** Ancora estimates the stock trades at an "unwarranted" discount to net asset value and values it at £12.36 ($16.40) per share

** Ancora said Blackstone BX.N had offered 50% above the current share price and that soliciting interest now could yield a higher offer

** As of last close, BYG was down 23.6% YTD

($1 = 0.7539 pounds)