* FTSE 100 up 0.2%, FTSE 250 flat
* Brexit deal vote on agenda
* Shell lower after Q4 update
* NMC Health on course for worst week ever (Adds news items, analyst comment, updates share prices)
Dec 20 (Reuters) - London's main index rose on Friday and was on course to record its longest winning streak in more than two-and-a-half years, as shares of exporters benefited from a subdued pound amid renewed no-deal Brexit worries.
The FTSE 100 inched 0.2% higher, tracking its best run of consecutive gains since May 2017. The FTSE 250 was flat at 0835 GMT as trading began to wind down ahead of the holiday season.
After a breakthrough in U.S.-China trade talks and Prime Minister Boris Johnson winning the British elections, investor focus now shifts to his vote on a divorce deal with European Union.
The euphoria around Johnson's win had triggered a rally in domestically-exposed stocks, though fears of a chaotic Brexit have re-emerged due to a new provision for a hard, December 2020 deadline to reach a trade agreement with the European Union.
However, sterling traded near two-week lows as traders expect the deal to be ratified without any major hiccups, helping exporter stocks such as Diageo and Reckitt Benckiser.
Despite swinging between sharp gains and losses this week, the midcaps, whose components earn most of their money at home, are still set for an eighth successive weekly jump.
Shell dipped nearly 1% after it forecast $2.3 billion in impairment charges for its latest quarter and trimmed its oil production sales outlook.
Shares of Just Eat fell 2%, a day after Dutch firms Prosus NV and Takeaway.com tabled their final offers for the company. Takeaway.com looks poised to win approval to buy the British online food delivery group.
"We... believe that (Takeaway's) new terms more appropriately value Just Eat, and it is more likely to pass than the improved cash offer from Prosus," a Liberum note said.
UAE-based NMC Health, targeted by short seller Muddy Waters, tumbled another 6%. Its stock has shed roughly 40% since Tuesday and is on track for its worst weekly performance ever. (Reporting by Shashwat Awasthi in Bengaluru; Editing by Subhranshu Sahu and Rashmi Aich)