(Adds London Stock Exchange)
July 31 (Reuters) - The following bids, mergers, acquisitions and disposals were reported by 2000 GMT on Wednesday:
**Some trading and investment firms are calling for competition regulators to scrutinise London Stock Exchange's LSE.L proposed $27 billion takeover of financial information provider Refinitiv to prevent further market data price hikes. EssilorLuxottica ESLX.PA is buying Dutch opticians group GrandVision GVNV.AS for up to 7.2 billion euros ($8 billion) in cash to take control of thousands of stores where it sells spectacles and lenses. Roche ROG.S and Spark Therapeutics ONCE.O announced another extension of the Swiss drugmaker's $4.3 billion takeover offer for the U.S. gene therapy specialist as regulatory reviews in the United States and Britain continue. Resolute Mining Ltd RSG.AX said it would buy West Africa-focused Toro Gold Ltd in a cash and stock deal worth $274 million, as the company looks to expand production amid a run of consolidation in the gold industry. Oil firm DNO DNO.OL is casting an eye over Exxon (NYSE:XOM) Mobil's XOM.N Norwegian assets as it looks for more deals after buying London-based peer Faroe earlier this year, its executive chairman said. Marijuana producer CannTrust Holdings Inc TRST.TO said it was exploring a possible sale, days after it fired its top boss following an investigation by Health Canada that showed the company grew cannabis in unlicensed rooms. Italian holding company CIR's CIRX.MI healthcare unit KOS has signed an agreement to buy 100% of German nursing home company Charleston for 90 million euros ($100 million), CIR said.