FTSE 100 rises on China stimulus hopes amid caution ahead of Brexit vote

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* FTSE 100 up 0.5 pct; FTSE 250 up 0.1 pct

* Investors await key Brexit deal vote

* Financials top support to main index

* Provident Financial (Other OTC: FPLPF - news) sinks after profit alert

Jan 15 (Reuters) - Britain's FTSE 100 opened slightly higher on Tuesday on hopes Beijing will take steps to stabilise a slowing economy, but investors remained cautious ahead of a crunch vote on Prime Minister Theresa May's Brexit plan.

The FTSE 100 was 0.5 percent higher by 0842 GMT and the domestically-focused FTSE 250 was up 0.1 percent, underperforming their European peers.

Many lawmakers are not convinced with assurances in Prime Minister Theresa May's draft deal and outcomes ranging from a disorderly divorce to a Brexit reversal could open up if Parliament votes the deal down, as is widely expected.

"Of course, we could get a situation where the vote gets passed, but given the polling numbers that looks about as likely as finding a unicorn," said CMC Markets (LSE: CMCX.L - news) analyst Michael Hewson.

In a last-ditch effort, May urged lawmakers on Monday to take a "second look" at her deal and warned parliament it risked the break-up of the United Kingdom if it voted against the agreement.

Banks, miners and oil majors led the early charge on the main index after China signalled more growth-boosting steps and oil prices rose amid supply cuts.

Asia-focused bank HSBC was the biggest boost to the FTSE 100, with miner Rio Tinto (Hanover: CRA1.HA - news) also a big support.

Gambling firms Paddy Power (EUREX: 27913021.EX - news) , GVC, William Hill, 888 Holdings slid between 0.7 and 3.2 percent after the U.S. Department of Justice issued an opinion that could further limit internet gambling.

Earnings drove direction among the top midcap movers.

Staffing company Hays (LSE: HAS.L - news) added 4 percent after higher quarterly net fees on the back of strong hiring in Germany while Spirent Communications (Frankfurt: 856880 - news) rallied 7 percent after forecasting better-than-expected full-year profits.

But sub-prime lender Provident Financial plunged 20 percent, on track for its worst day since Augus 2017, after a profit warning. The stock is on track for its worst day since August 2017.

(Reporting by Shashwat Awasthi and Muvija M in Bengaluru)