(For a Reuters live blog on U.S., UK and European stock markets, click LIVE/ or type LIVE/ in a news window) * FTSE 100 flat, FTSE 250 adds 0.1% March 31 (Reuters) - London’s FTSE 100 was unchanged on Wednesday, as weakness in healthcare and banking stocks countered gains in mining shares, while food delivery company Deliveroo slumped 30% on its first day of trading. The blue-chip FTSE 100 index was flat, with healthcare stocks, including AstraZeneca and GlaxoSmithKline, falling between 0.4% and 0.8%. Oil heavyweights BP and Royal Dutch Shell were also among the biggest laggards. The domestically focused mid-cap FTSE 250 index was up 0.1%, led by financial stocks. Topps Tiles fell 1.4% after reporting lower half-year sales, but the tile retailer said it expects sales to rise “sharply” and margins to recover to normal levels as the current lockdown in the United Kingdom gradually eases by the middle of April. Shares in Deliveroo opened well below the price of their initial public offering on Wednesday, and fell as much as 30% to 275 pence after making one of the most anticipated London stock market listings.