The FTSE 100 and the FTSE 250 were up 1.1 percent each by 0949 GMT after hitting their highest since Dec. 19. Post-holiday turnover remained low, with just 12 percent of the 90-day average daily volume traded in the first two hours.
The midcaps were on track for their biggest weekly gain in two months, showing some resilience to a slew of bad macroeconomic and corporate news from China and the United States in the first few days of 2019.
Beijing said it would hold vice ministerial level trade talks with Washington next week, pushing Asian shares higher and easing nerves of investors who have worried the tussle between the world's two largest economies will slow the global economy.
British stocks with more exposure to Asia rose as a result, with HSBC and Standard Chartered adding 1.1 percent and 2.7 percent, respectively, while luxury goods maker Burberry gained 2.1 percent.
Whitbread shares rose 2 percent after Barclays raised its rating and said the restaurant and hotel owner was its preferred hotel pick, while J Sainsbury fell 2 percent after a HSBC downgrade.
Mondi rose more than 3 percent after Jefferies said the company was its top pick in the paper and packaging sector for the current year.
Oil prices also edged up after news of the upcoming trade talks, boosting heavyweights BP and Shell by 1.9 percent and 1.5 percent.
Miners saw some comeback after a dismal last session, with Glencore, Rio Tinto, BHP and Antofagasta all gaining on the back of higher copper prices.
There was little news on mid-cap components and oil firms topped the gainers, although the index is likely to come into focus soon as a parliamentary vote on Prime Minister Theresa May's disputed Brexit deal is on the horizon.
A survey on Friday showed that a majority of May's Conservative Party members oppose her Brexit deal with the European Union, with less than three months until Britain leaves the European bloc.
Elsewhere, house-builder shares shrugged off a dismal house price data and gained on the Times report https://www.thetimes.co.uk/edition/bricks-mortar/what-2019-has-in-store-for-house-prices-l78d8wd7h that said demand may improve if a Brexit deal is struck.
Persimmon, Berkeley, Barratt and Taylor Wimpey all rose 1.3-1.7 percent on the main index while mid-caps Bovis Homes, Crest Nicholson rose 2.8 percent and 2.4 percent, respectively.
"Any chance, however slim, that either the current deal may survive, or even perhaps that Brexit effectively doesn't happen, supports Brexit-sensitive sectors like homebuilders," said Ken Odeluga, City Index analyst.
However, there was little optimism as data on house prices, consumer lending, mortgage approvals and services sector all pointed to a slowdown ahead of Brexit in the world's sixth-largest economy.
Circassia Pharmaceuticals tanked as much as 16 percent to record lows after the small-cap stuck to its 2019 targets ahead of a shareholder meeting later in the day.
AIM-listed Gear4music, which touts itself as UK's largest musical instruments and equipment retailer, sank nearly 50 percent on track for its worst day after saying it expects lower 2019 core earnings.