The FTSE 100 had lost some of its early momentum by lunchtime with the index trading 0.4% higher at 6,974.59 having flirted with the 7,000 level earlier on.
Sentiment was helped by stronger-than-anticipated economic data, with British gross domestic product falling 1.5% in the first quarter, beating expectations of a 1.6% drop.
Alcoholic drinks maker Diageo (DGE) gained 3.1% to £32.875, on announcing that it would initiate the second phase of £4.5 billion capital return program, but extend its duration by two years to 30 June 2024.
The welcome move came as Diageo forecast organic operating profit growth to be at least 14% in its current financial year, slightly ahead of organic net sales growth.
Healthcare services provider UDG Healthcare (UDG) soared 22% to 1.031, having upgraded its annual earnings guidance as improving margins in the first half helped offset weaker revenue.
UDG's pre-tax profit for the six months through March rose 5% to $65.1 million and the company forecast full-year adjusted earnings per share growth of 10-12%, up from 9-11% previously.
Travel company TUI (TUI) shed 3.6% to £412.40 as it racked up a €1.50 billion first-half loss while the pandemic continued hammer the tourism sector.
TUI said it had a pipeline of 2.6 million customers booked for the summer 2021 season, with a re-opening portfolio focused on destinations such as Greece, Balearics and the Canaries.
Also in the upgrade club was motoring services group Redde Northgate (REDD), which climbed 4.1% to 380.1p following a strong second-half sales performance.
Redde Northgate's underlying pre-tax profit for the year through April was now expected to be 'moderately above' the top end of the current range of analyst estimates, and not less than £92 million.
Thermal energy management and niche pumping specialist Spirax‐Sarco Engineering (SPX) also impressed, gaining 3% to £119.05. Its margins in the year to date were higher than expected amid a strong performance at Watson-Marlow.
Organic sales growth in the four months through April beat global industrial production, Spirax‐Sarco said, as Watson-Marlow enjoyed strong vaccine-related demand for pharmaceutical customers.
Molten metal flow engineering group Vesuvius (VSVS) dipped 0.3% to 578p after it guided for a full-year trading profit 'moderately' ahed of market expectations.
Vesuvius said the current consensus forecast for annual earnings before interest, tax and amortisation was £138 million, the company said in a trading update for its annual general meeting.
Landscape products group Marshalls (MSLH) rallied 2.5% to 740.5p, having upgraded its annual guidance, too, amid a 46% jump in year-to-date sales.
Marshalls said it now expected trading for the full year through December to be 'ahead of its previous expectations'.
Elsewhere, food services group Compass (CPG) fell 1.1% to £15.12, even as it reported a slump in first-half profit owing to the pandemic impact, but said it expected a gradual improvement in the third quarter.
Defence contractor Ultra Electronics (ULE) firmed 0.9% to £20.34 on reporting flat revenue growth so far in 2021. The company continued to forecast 'another year of good progress'.
Bus and train group National Express (NEX) was flat at 298.5p after it said it was continuing to post operating profits, thanks to cost cutting and a recent improvement in sales.
National Express's revenue for the four months through April was down 16% year-on-year, though during the month of April it was up 50% year-on-year.