* FTSE 100 down 0.5%, FTSE 250 down 0.3%
* Miners biggest drag after Rio Tinto 's output cut
* Ocado biggest blue-chip faller
* Saga at record low after poor trading update
* CYBG gains after Virgin Money (LON:VM) rebrand plans (Adds news items, analyst comment, updates to closing prices)
June 19 (Reuters) - Britain's main index slipped on Wednesday, weighed down by miners after Rio Tinto cut its forecast for shipments from an Australian region, while sterling's gains ahead of Bank of England meeting dragged down exporters.
The FTSE 100 index .FTSE dipped 0.5%, its worst fall this month, while the FTSE 250 midcap index .FTMC was down 0.3%. The indexes handed back some gains from Tuesday after a dovish policy speech by European Central Bank chief Mario Draghi.
Anglo-Australian miner Rio Tinto RIO.L fell 4.7% after it lowered its outlook for shipments from a hub in the Pilbara region in Australia due to a higher proportion of certain lower grade products. had a knock-on effect on rivals as well, dragging the sectoral index .FTNMX1770 nearly 3% lower to its worst day in more than six months.
Online grocer Ocado OCDO.L fell nearly 6% to the bottom of the FTSE 100 index with a trader saying it was because of negative sentiment stemming from a media report on stiff competition in the quick delivery industry as Amazon.com AMZN.O tied up with Morrison MRW.L .
Upmarket food retailer Marks and Spencer MKS.L dropped 4.5% after Tesco TSCO.L said it was considering a trial of an upmarket convenience store under the "Tesco finest" banner. American Tobacco BATS.L , Unilever ULVR.L and Reckitt Benckiser RB.L , which get a chunk of their revenue in U.S. dollars, weakened as the pound rallied before the BoE policy meeting where it might strike a relatively more confident tone than its counterparts.
All eyes are now on the conclusion of the U.S. Federal Reserve's two-day meeting after markets close.
British Airways owner IAG ICAG.L fell 3.2%, after earlier touching a two-and-a-half-year low, and easyJet EZJ.L dropped 2.6%. HSBC downgraded the stocks after German airline Lufthansa's profit warning this month.
"We are increasingly cautious towards European airlines ... expect many will follow Lufthansa's profit warning," HSBC analysts wrote. They also forecast weakness in long-haul and corporate travel demand in Europe.
Online takeaway service Just Eat JE.L lost 3.7% after a rating cut by UBS.
British American Tobacco BATS.L and Imperial Brands IMB.L weakened after Nielsen data indicated that UK retail cigarette sales fell in May. midcaps, insurance and tourism firm Saga SAGAG.L plunged 12.1% to a record low after warning that its tour operations were still being undercut by political uncertainty in Britain. retailer Ted Baker TED.L slumped 9% to a record low after HSBC slashed its price target by more than half to lowest compared to other brokerages. and Yorkshire Banking Group CYBGC.L , however, jumped 6.2% after the lender laid out plans to challenge Britain's big banks, betting that a re-brand as Virgin Money will help it shake up the market.