The stock rose 2% as it said the overseas push would grow international sales by a quarter and profits by 40% - providing a welcome distraction to ongoing struggles in its domestic UK market.
The wider FTSE 100 Index climbed narrowly, by 6.4 points, to 6659, helped by gains among heavyweight miners after an earthquake off the coast of major copper producer Chile sent metals prices higher.
London's blue chip share index was also boosted by more record highs set on Wall Street overnight after new signs of life in the US manufacturing sector.
Germany's Dax and France's Cac 40 also saw small gains while New York's Dow Jones Industrial Average was ahead at the time of the close in the City.
On currency markets, sterling held firm at $1.66 and €1.21.
In London, M&S was up 10.1p to 469.9p after setting out its aims, at an investor and analyst presentation in Paris, to open a raft of stores outside the UK over the next three years, including 20 food stores across the French capital.
But supermarkets Tesco and Morrisons were on the back foot after a gloomy broker note from HSBC on the stocks.
Bradford-based Morrisons shed nearly 2% or 3.6p to 207.2p, while market leader Tesco eased 0.8p lower to 292.6p.
Elsewhere, online retailer ASOS was also in the spotlight after its half-year results confirmed a 22% drop in profits to £20.1 million as it took a hit from expansion costs.
But shares ended 27p up at 5181p after assurances from boss Nick Robertson that the investment programme would double annual sales capacity up to £2.5 billion.
Blue chip insurers were also in the red as major players gave back some of the rises seen in the previous session's bounce-back amid the furore over the Financial Conduct Authority's botched announcement of an inquiry into 30 million closed financial policies. Aviva and Resolution were impacted further after going ex-dividend, meaning new shareholders are no longer entitled to the latest pay-out.
Resolution dropped 5% or 15.3p to 288.4p and Aviva fell 4.3p to 487.8p.
Bus and rail firm FirstGroup slipped 1% or 1.7p to 137.3p in the FTSE 250 after revealing operating profits would be £14m lower than expected due to recent severe weather conditions, especially in the US where it runs First Student and Greyhound.
The biggest FTSE 100 risers were Fresnillo, up 31p to 877p, Mondi up 32p to 1073p, International Airlines Group up 12p to 436.5p.The biggest FTSE 100 fallers were Resolution, down 15.3p to 288.4p, Pearson down 30p to 1014p, Hargreaves Lansdown off 26p at 1424p and Morrisons down 3.6p to 207.2p.