LONDON, Dec. 10 (Xinhua) — London stock market went up by midday on Thursday with the FTSE 100 index gaining by 26.16 points, or 0.50 percent, at 5,230.05 points at 12:10 GMT.     Shares in DS Smith were up by 10.48 percent, the biggest winner by noon. And shares in Royal Bank of Scotland Group and Lloyds Banking Group also increased by 5.36 percent and 4.57 percent respectively.