The FTSE 100 and the mid-cap FTSE 250 were up 0.2% by 0805 GMT.

China's iron ore prices have hit record highs this week amid rising concerns about shrinking stocks and worries about the risk of another Brazil mine dam collapse.

Rio Tinto and BHP were among the top boosts to the main FTSE index.

Still, investors returned from an extended weekend to continued uncertainty over China's trade dispute with the United States, after U.S. President Donald Trump said on Monday Washington was not ready to make a deal with Beijing but that he expected one in the future.

Healthcare provider NMC Health rose 3.7% on the FTSE 100 after hiking its 2019 revenue and core earnings targets.

Brexit-sensitive stocks such as retailers and housebuilders, which took a hit last week ahead of Prime Minister Theresa May's announcement that she would resign, also recouped some losses on Tuesday.

"The UK is sort of stuck in limbo, unable to fully move forward with anything Brexit-related until the next PM is found," Spreadex analyst Connor Campbell said.

Shares of mid-cap builder Galliford, one of those to have suffered from the collapse of major government contractor Carillion last year, surged 6.5% after news emerged of a rebuffed offer for two of its units from Bovis Homes .

Shares of Bovis, which said it was "no longer in talks" over the purchases, were roughly flat.

Tour operator Thomas Cook, hammered last week by worries over its cashflow and summer sales, advanced 7.8% after Berenberg raised its rating to "hold" from "sell", citing the bids the company has said it has received for its airline unit.

"The deterioration in Thomas Cook's financial position leaves the company looking for a white knight to pay a fairly punchy multiple for the airline," Berenberg analysts wrote.