* Oil stocks & miners lead FTSE 100 gains

* GSK spin-off Haleon falls on debut

* Euromoney surges on buyout offer

* Direct Line slides on downbeat outlook

* FTSE 100 up 0.9%, FTSE 250 adds 1.0%

July 18 (Reuters) - Britain's FTSE 100 rose on Monday lifted by commodity stocks and an upbeat global mood, while shares of Haleon, spun off from drugmaker GSK, fell on their debut on the London Stock Exchange.

The commodity-heavy FTSE 100 ended 0.9% up after rising as much as 1.5%.

European markets trimmed some early gains after Russia's Gazprom declared force majeure on gas supplies to Europe to at least one major customer.

"What we're seeing is just the spillover effect from the Friday rebound," said Michael Hewson, chief market analyst at CMC Markets UK.

"We still have to be cautious about it because there are a lot of moving parts as can be seen from the story of Gazprom calling force majeure."

Oil majors Shell and BP were the biggest boost to the FTSE 100, rising more than 2% each, as crude prices jumped on a weakening dollar and fears of tight supplies from Russia.

Mining giants Glencore and Rio Tinto rose 2.9% and 3.2%, respectively, as metal prices rose on Chinese regulators' measures to avert a potential crisis in the country's real estate market and a softer dollar.

However, investors remained cautious ahead of earnings this week in Europe amid soaring inflation, slowing economic growth and political uncertainties.

Investors are also focused on a slew of data this week, including the UK employment report, inflation and retail sales numbers which could offer clues on the health on the economy and monetary policy outlook.

The domestically focused midcap index climbed 1.0%, its highest level since June 30.

Drugmaker GSK's spinoff Haleon fell 6.6% on debut after it started trading at 330 pence, giving it a market valuation of around 31 billion pounds ($37.00 billion). Shares of GSK were flat.

Euromoney surged 9.5% after a group led by French investment firm Astorg Asset Management said it would offer to buy the business-to-business information company in a 1.66 billion pound ($1.97 billion) deal.

Direct Line tumbled 10.5%, as the car insurer revised downwards its profitability outlook for the year. (Reporting by Sruthi Shankar and Bansari Mayur Kamdar in Bengaluru; Editing by Rashmi Aich and Alison Williams)