* FTSE 100 up 0.3%, FTSE 250 up 0.4%
* Oil giants gain, offset some trade worries
* Mid-cap FirstGroup hits near 2-yr high
* Daily Mail publisher surges on upbeat results
* De La Rue sinks to over 14-yr low after profit warning (Adds news items, analyst comments, updates share prices)
May 30 (Reuters) - Gains in heavyweight oil company shares helped London's main index inch higher on Thursday even as some aversion to risky assets prevailed after Beijing dialled up the rhetoric against Washington in their protracted trade war.
The FTSE 100 rose 0.3% by 0745 GMT. The mid-cap FTSE 250 gained 0.4%, helped in part by a 12% surge in rail and bus operator FirstGroup.
Oil majors Shell and BP boosted the main share index as oil prices rose on Thursday after an industry report showed a bigger-than-expected decline in U.S. crude inventories, though global trade uncertainty still looms.
Markets have been bracing for the possibility that a resolution to the Sino-U.S. spat may not be imminent. China fired another shot at the United States on Thursday as Vice Foreign Minister Zhang Hanhui said provoking trade disputes was "naked economic terrorism".
"There's still lots of nervousness out there and the downward pressure is rather powerful and looks hard to resist. Any gains look hard won and easy to give up at the moment," Markets.com analyst Neil Wilson said.
The blue-chip bourse rose after two sessions of losses, but gains were capped somewhat by a 4.6% drop in energy utility National Grid and 3.3% slip in retailer Marks & Spencer as both stocks traded ex-dividend.
Johnson Matthey also shed 3% after the chemicals group's annual profit missed consensus estimates.
FirstGroup, under pressure from a shareholder to make strategic changes, jumped to a near two-year high after it put its U.S. coach service Greyhound up for sale and also said it was looking to separate its UK First Bus operations.
"Greyhound is in long term structural decline and absorbs considerable management time without offering upside potential, and therefore disposing of it is optimal," Investec analysts wrote.
Among smaller stocks, De La Rue Plc lost a quarter of its value and plummeted to a more than 14-year low, after the banknote and passports maker warned of "somewhat lower" profit in fiscal 2020 and said its chief executive would step down.
But Daily Mail and General Trust jumped 10% on the pan-regional STOXX 600 <.STOXX< after the Daily Mail publisher reported a better-than-expected rise in first-half profit and reaffirmed its annual forecasts. (Reporting by Shashwat Awasthi in Bengaluru; Editing by Alison Williams)