UPDATE 1-UK stocks battered as PM May delays Brexit vote

* FTSE 100 down 0.8 pct; FTSE 250 at Dec 2016 lows

* PM May pulls vote on her divorce deal

* Housebuilders, banks lead losers as Brexit uncertainty grows

* Utilities, Royal Mail also fall on election worries

* Interserve sinks to record low on rescue plan outline (Recasts, adds details, closing prices)

By Danilo Masoni

MILAN, Dec 10 (Reuters) - British shares fell on Monday as a delay to a parliamentary vote on Prime Minister Theresa May's Brexit deal threw the country's political future into the unknown, hitting the pound and domestically-exposed companies from housebuilders to banks.

The delay to the vote which had been due on Tuesday opened a range of options for Europe's No.2 economy, including a disorderly Brexit, another referendum on European Union membership, or a last minute renegotiation of May's deal. internationally exposed stocks such as British American Tobacco (JO: SNHJ ) and GlaxoSmithKline were lifted by the pound falling to 20-month lows but their gains were more than offset by a broad sell-off led by companies more exposed to the domestic economy.

"The only known is that the uncertainty has increased and we are faced with more volatility for sterling and UK assets," said Neil Wilson, Chief Market Analyst at Markets.com.

The FTSE 100 .FTSE top share index fell 0.8 percent, while the more domestically focused FTSE 250 .FTMC index tumbled 2 percent, sliding back to its lowest level since December 2016.

Financials were the biggest drag on the FTSE with domestically focused banks Royal Bank of Scotland RBS.L and Lloyds LLOY.L falling 2.1 and 3 percent respectively. They underperformed banks with broader international presence such as HSBC HSBA.L and Barclays BARC.L , both down less than 1 percent.

Housebuilders, which are also highly sensitive to Brexit developments, were down sharply as tension built and analysts at Peel Hunt cut their ratings and price targets. in Berkeley Group BKGH.L , Persimmon PSN.L , Taylor Wimpey TW.L and Barratt Developments BDEV.L fell between 3.5 and 5.1 percent, all extending earlier losses after May delayed the vote in parliament.

Utilities Centrica CNA.L and SSE SSE.L , down 4.6 and 3.6 percent, were also weighed down by political uncertainty .

Analysts say the prospect of a government led by the opposition Labour party should May's Conservative administration collapse and a consequent threat of a nationalisation of utilities would put further pressure on the sector.

Royal Mail RMG.L , recently demoted from the FTSE 100, also fell 2.3 percent.

"Remember that Labour had previously threatened to nationalise utilities and Royal Mail, so investors may be starting to price in a higher likelihood of a general election in the near future and for Labour to have a strengthening hand," said Russ Mould, investment director at AJ Bell.

Traders said Centrica was also hurt after the Sunday Telegraph reported that the owner of Britain's largest energy supplier British Gas could struggle to pay dividends.

Shares in pension provider Just Group JUSTJ.L rallied 19 percent, scoring its best day ever, following a policy announcement from the Bank of England's regulatory body that proposed changes in rules over lifetime mortgages. appears a good announcement for Just Group and removes a considerable amount of the uncertainty faced by shareholders," said Numis in a note.

Among the few other gainers were shares in precious metal miner Randgold RRS.L , which was lifted 5.5 percent as investors sought refuge in safe haven assets such as gold.

Shares in Interserve IRV.L plunged 53 percent to fresh record lows after the embattled British outsourcer announced a rescue plan that envisaged converting much of its debt into new shares, potentially handing control of the company to its creditors.