The blue-chip FTSE 100 added 0.1% by 0739 GMT, while the midcap FTSE 250 index also inched 0.1% higher.
The mood was dull in Asian and European stock markets, with investors turning to defensive sectors such as healthcare and consumer staples amid worries about the health of the world's second-largest economy.
AstraZeneca gained 1.9% after the drugmaker said its cancer drug, Enhertu, developed with Japan's Daiichi Sankyo delayed the progression of a form of advanced breast cancer in previously treated patients.
Oil major Shell, and miners Rio Tinto and Anglo American slipped, in tandem with weaker commodity prices. [O/R] [MET/L]
(Reporting by Sruthi Shankar in Bengaluru; editing by Uttaresh.V)