Britain's FTSE 100 retreated slightly on Thursday after downbeat euro zone PMI data and as investors booked profits before the long Easter weekend.

The FTSE 100 was down 0.2 percent and the FTSE 250  dropped 0.1 percent. Despite being in the red this session, both indexes ended the week in positive territory.

"What's clear from today's PMI numbers is that there are as yet no green shoots of spring for the euro zone," Markets.com analyst Neil Wilson said.

Euro zone business activity barely grew in April as demand was sluggish even though prices rose modestly, surveys showed. Germany's Purchasing Managers' Index suggested a contraction among manufacturers in Europe's largest economy would continue for a few more months at least.

"If Europe is still struggling, then we're not going to see any significant pick-up in UK stocks, certainly not the more global ones, because we need to sell them stuff," CMC Markets analyst Michael Hewson said.

Unilever was a stand-out gainer, rising 2.9 percent to levels not seen in a year and a half on the back of stronger-than-expected quarterly sales.

Jefferies analysts called the quarter a "decent start" to the year.

The FTSE 100 was dragged lower by AstraZeneca and GlaxoSmithKline, which fell following a sell-off in U.S. healthcare stocks over regulatory worries on Wednesday.

British American Tobacco shed 1.4 percent and Imperial Brands gave up 0.8 percent after U.S. Senate Majority leader Mitch McConnell said he plans to introduce legislation to raise the minimum age for buying tobacco products.

Britain's biggest defence company BAE Systems, which was trading ex-dividend, lost 3.8 percent.

Oil majors Shell and BP dropped on the FTSE 100, while Petrofac tumbled 10.8 percent on the mid-cap index.

The FTSE 250 was also dragged down by stocks trading ex-dividend. Motor insurer Hastings and power producer Drax were among the worst performers.

But price comparison website Moneysupermarket.com and cybersecurity firm Avast jumped 4.3 percent and 5.8 percent, respectively, after their first-quarter revenue climbed.