The main index added 0.8 percent while midcaps were up 1 percent, after ending lower on Friday as fresh concerns over the Sino-US trade situation added to fears of a slowdown in the world economy.
Overseas, gains on Wall Street were led by industrial companies as a new round of talks between the United States and China piqued hopes for a trade deal.
Asia-focused bank HSBC rose 1.5 percent.
Travel group TUI's London-listed shares advanced 5 percent to top the FTSE 100 leader-board as traders cited Bank of America Merrill Lynch resuming coverage with a "Buy" rating.
Imperial Brands was 2 percent higher after the tobacco group said its non-executive chairman Mark Williamson would step down. Larger rival British American Tobacco also rose 2.7 percent.
The gain in the FTSE 100, coming after three sessions of losses, marked a strong start to a week in which British Prime Minister Theresa May is due to update parliament on her progress towards a European Union divorce deal.
The market held up despite data showing the British economy had slowed in the final three months of last year, pushing growth in 2018 to its weakest in six years, as Brexit worries hammered investment.
The contraction, however, was as expected and came after economic growth forecast cuts by the Bank of England and the European Commission last week.
As the March 29 exit date ticks closer, a deal on how the world's sixth-largest economy will leave the European Union is still in limbo and companies are reigning in spending until the fog clears.
May has rejected the idea of targeting a customs union with the EU, stamping out hopes that she could shift her Brexit policy to win over the opposition Labour Party.
"Clearly the Brexit discussions - and the need for a compromise to be forged - are a source for further concerns or an opportunity to quell the malaise with huge implications for all UK consumers, employees, employers and the general economy," Raymond James analyst Chris Bailey said of the data.
After touching their highest since November on Chinese iron ore futures hitting record levels, metals stocks shed some gains to end up 1 percent, even as most base metals prices fell on global growth worries.
Among mid-caps, the biggest boost came from takeaway group Just Eat, which climbed 4.4 percent after its shareholder Cat Rock Capital Management urged the company to start merger talks and said it would benefit from a deal rather than relying on a new chief executive officer.
Metro Bank, whose stock has roughly halved in value following an accounting error, surged 6.5 percent stand among top mid-cap gainers following a Berenberg upgrade.
Among a handful of losers was Smith & Nephew which slid 3 percent after the Financial Times reported that it has held talks to buy US-based medical equipment maker NuVasive in a deal that would be worth more than $3 billion.
Small-cap KCOM rose 6.1 percent after the Telegraph reported that Virgin Media was considering a takeover bid, while logistics firm Connect Group rose 3 percent on a contract with Daily Mirror publisher Reach Plc.