London's FTSE 100 dipped to a one-month low on Wednesday as oil majors dived after US inventories bulked up and a rise in pound knocked exporters, but gains in Sainsbury's and LSE following upbeat results helped cushion the fall.

The FTSE 100 ended 0.4 percent lower and the more domestically-focused FTSE 250 inched down 0.1 percent.

Shell shed 1.4 percent to a month low and BP gave up 2.1 percent, as crude prices weakened after US oil inventories rose more-than-expected with output reaching a new record of 12.3 million barrels per day.

As sterling rose to multi-week highs with lingering hopes of progress in cross-party Brexit talks and ahead of Bank of England interest rate meeting on Thursday, exporter companies bore the brunt as much of their revenue is earned in dollars.

British American Tobacco, AstraZeneca, GlaxoSmithKline were among the biggest drags.

Contrary to the mood in Britain, the S&P 500 index notched a fresh record high on the Wall Street as gains in Apple after forecast-beating results thrust up technology stocks.

Among big fallers on UK's blue-chip index was Takeaway group Just Eat with a near 3 percent drop after JP Morgan called European rivals Delivery Hero and Takeaway.com more attractive.

Education group Pearson lost 2.1 percent after news of a planned merger between Cengage and McGraw Hill, with Liberum analysts calling the planned deal a "major headache" for Pearson.

However, earnings reports boosted many blue-chips.

Sainsbury's jumped 4.3 percent after the supermarket group's underlying full-year profit beat market estimates and it said it would accelerate investment in its store estate and technology.

London Stock Exchange climbed 3.4 percent after it reported higher quarterly income, as its clearing and information services businesses grew strongly against what it called a challenging market backdrop.

Lloyds rose 1.6 percent after it cut its target for its Common Equity Tier 1 ratio - a closely watched measure of balance sheet strength, with Goodbody analyst John Cronin saying that meant more headroom for distribution to investors.

But that was not enough to keep the main bourse out of the red, as a surprise fall in United States construction spending in April also weighed on the index.

Markets also awaited the US Federal Reserve's policy statement scheduled for later in the day and Chairman Jerome Powell's press conference shortly afterwards.

Overall trading volumes were slim as many markets elsewhere in Europe were closed for a May 1 public holiday.