The FTSE 100 was up 0.3 percent and the FTSE 250 rose 0.4 percent by 0841 GMT.
Both followed gains in Asia after data showed that new home prices in China grew slightly faster in March after a slow-down the previous month, kindling hopes that Beijing's stimulus measures were having an impact.
Hopes that the Sino-US trade dispute would soon be resolved also gave some support as investors waited for growth figures from the world's top metals consumer. Miners as well as Asia-exposed financial heavyweights HSBC and Prudential boosted the main bourse.
"Hopes towards what the Chinese GDP numbers might say tomorrow (Wednesday) combined with a more positive interpretation from the IMF's Spring meeting over the weekend have helped perceptions towards growth-sensitive sectors like miners and banks," said Raymond James analyst Chris Bailey.
Bailey added that slowing volumes and a lack of any overtly bad political news could also be helping shares glide higher.
The FTSE 100 did trim gains slightly after data showed British workers' pay grew at its joint fastest pace in over a decade, driven by further job creation, adding to suggestions that Brexit uncertainty is prompting firms to hire workers rather than make longer-term investment in equipment.
Among a handful of blue-chip losers was Sainsbury's which gave up 1 percent after brokerage Bernstein cut its price target and said it could not consider the stock as a "buy-case".
On the FTSE 250, Galliford Try slumped 18 percent to its lowest since August 2012 after saying it was undertaking a strategic review of its construction business which would reduce its size and lead to a fall in annual profit.
But helping the mid-caps post carve out gains was JD Sports Fashion which added 4.8 percent and hit an all-time high as acquisitions helped it tackle a challenging retail environment at home and post better-than-expected full-year earnings.
Emerging market-focused asset manager Ashmore rose 3.5 percent after reporting a double-digit jump in assets under management and Card Factory rose about 5.6 percent after its annual results.
Hays shed 3.3 percent as the recruitment firm's organic growth in Australia and Germany slowed in the third quarter.