The main index added 1 percent while midcaps were up 0.6 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.
All sectors across the board were positive by 0951 GMT.
Monday's rise 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 still in limbo and companies are reigning in spend 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.
"It does rather seem like she is trying to bounce parliament into a last minute choice between her deal or no deal at all. As the clock counts down the risk is that the delaying tactics backfire and the UK leaves without a deal," said Markets.com analyst Neil Wilson.
Miners climbed to their highest since November with Chinese iron ore futures at record highs on concerns that supply from Brazil, the country's second-largest ore supplier, may decline after a fatal dam accident at a Vale mine.
Travel group TUI's London-listed shares jumped 4.1 percent to top the FTSE 100 leader-board as traders cited Bank of America Merrill Lynch resuming coverage with a "Buy" rating. The gains erased some of the steep losses of last week after poor results.
Takeaway group Just Eat rose 2 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.
Elsewhere, Chinese shares rose ahead of a new round of trade talks with the United States that started on Monday. Asia-focussed bank HSBC rose 1.6 percent and was the biggest support to the blue-chip index.
Oil majors BP and Shell were also among top gainers on the back of higher crude prices.
Among a handful of losers was Smith & Nephew which slid 3.4 percent to be the worst FTSE 100 performer. 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 advanced 10 percent after the Telegraph reported that Virgin Media was considering a takeover bid, while logistics firm Connect Group rose 4 percent on a contract with Daily Mirror publisher Reach Plc.