The FTSE 100 was up 0.45 percent at 7,697 points by 0810 GMT, following a flat close in the previous day when worries over Britain's exit from the EU weighed. The mid-cap index FTSE 250 added 0.1 percent.
"Though it still couldn't break out of its recent trading bracket, the FTSE at least pushed to the upper end of it after the bell. The index's main boost came from the commodity sector," said Connor Campbell, analyst at Spredex.
Oil major BP and miners Rio Tinto, BHP and Glencore rose between 1.4 and 2.1 percent as oil prices rose with re-introduced US sanctions against major crude exporter Iran expected to tighten global supply.
Metal prices also gained with copper prices edging higher, aided by a weaker dollar.
The biggest moves, however, were among companies which reported results, most of which disappointed investors.
Shares in Intertek fell 6.8 percent to the bottom of the FTSE after first-half earnings at the product testing company fell short of market expectations.
Analysts at Jefferies affirmed their buy rating on the stock, saying margins were still good, although they expected consensus estimates to be slightly trimmed to reflect the acquisition of training software form Alchemy last week.
Shares in Hargreaves Lansdown fell 3.5 percent, as waning confidence among investors and rising costs took the shine off a record-breaking year for British fund supermarket.
Hargreaves said total assets rose 16 percent to a record 91.6 billion pounds in the year to the end of June. Some analysts said the flows had lagged forecasts.
InterContinental Hotels Group was also among the top fallers, following its results.
Mid-cap Domino's Pizza reported an increase in overall half-year sales, but profits were weighed down by investments overseas, sending its shares down more than 9 percent.
"Whilst the stock has already been weak into results, we believe the slower LFL (like-for-like) growth, weaker profit growth and store opening run-rate will be a concern," said UBS analysts. The stock led mid-cap fallers and was set for its biggest one-day fall since March 2017.