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* FTSE 100 flat, FTSE 250 adds 0.4%

* Both FTSE 100, FTSE 250 eye weekly gains

* Trainline tops mid-caps

* December Composite PMI at 51.7 vs 50.9 estimate

Dec 15 (Reuters) -

The UK's FTSE 100 was flat on Friday as losses in healthcare stocks offset rising resources-linked shares, while the index eyed weekly gains in an action-packed week dominated by interest rate decisions from major central banks.

The blue-chip FTSE 100 held steady at 7,651.31 points as of 0932 GMT, while the FTSE 250 midcap index added 0.4%.

Investor sentiment was bolstered this week after the U.S. Federal Reserve signalled that it could pivot to rate cuts next year, setting the exporter-heavy FTSE 100 on track for its third straight weekly gain, while the mid-cap index is likely to post sharp weekly advances as well.

"(The markets) are pricing in quite a lot for 2024 and that goes well beyond what our economists are expecting in terms of cuts for next year, but the pivot from the Fed is significant," said Sphia Salim, head of European rates research at BofA Global Research.

However, the Bank of England (BoE) and the European Central Bank both hinted on Thursday that rates would remain higher for longer.

"There's a desire from the market to pricing some synchronized easing cycle to some extent, but we do believe that the Bank of England has a much bigger inflation problem at hand," added BofA's Salim.

Goldman Sachs said it expects the BoE to deliver its first rate cut in June, compared to a previous expectation of August.

On the day, industrial metal miners jumped 2.3%, while heavyweight energy stocks climbed 0.9% on higher crude oil prices.

Capping gains, however, drugmaker AstraZeneca dropped 1.6% after rising for the last three sessions.

Among individual stocks, Trainline surged 15.4% following news that the UK government has ditched plans for a centralised online rail ticket retailer.

Meanwhile, a preliminary reading showed companies in Britain's services sector witnessed another pick-up in growth this month. (Reporting by Shashwat Chauhan in Bengaluru; Editing by Sherry Jacob-Phillips and Sonia Cheema)