The FTSE 100 added 0.3% and the mid-cap FTSE 250 was little changed by 0805 GMT.
Luxury brand Burberry jumped nearly 8%, set for its best day in nearly seven years, after it posted a stronger-than-expected rise in first-quarter comparable-store sales and affirmed its annual forecast.
"The big question facing Burberry has been to what extent the Chinese consumer is reining in their luxury buying ... Not so much, it seems," Markets.com analyst Neil Wilson said, as the company's revenue growth in China and across Asia improved.
Airline stocks climbed after Ryanair said deliveries of Boeing's 737 MAX planes may be delayed further, raising the prospects of over-capacity in Europe would ease.
"It's just that reduced capacity is what is required for the industry - improved pricing environment which should be supportive of margins," Wilson said.
Shares of Europe's largest budget carrier, which cut its forecast for growth in traveller numbers next summer, rose 1.1%. British Airways owner IAG gained 1% and mid-cap easyJet added 2%.
A.G.Barr tumbled almost 30% on the mid-cap index and was on track for its worst day ever, after the Irn-Bru maker warned that its annual profit would sink 20% compared with last year. Soft-drink makers Fevertree and Britvic fell 2.5% each.
Sterling fell amid concern that eurosceptic Boris Johnson will become Britain's next prime minister and on earlier hints the Bank of England would cut interest rates. Companies that book much of their revenue in dollars, such as BAT, benefited as a result.
Investors also eyed U.S. retail sales data and more corporate earnings reports to assess the health of the world's largest economy and the outlook for rate cuts by major central banks.
Education company Pearson advanced 2.8% after saying it would break from the conventional and more expensive textbook publishing model and release U.S. college textbooks in digital form first.
The proposed change in Britain's discount rate used to calculate compensation for personal injuries led motor insurer Hastings to forecast a pre-tax charge for 2019, sending its shares nearly 5% lower.