UPDATE 2-FTSE 100 hits one-month high; Brexit tussle bogs down midcaps

* FTSE 100 up 0.7%, FTSE 250 flat

* Oil, miners drive gains on main index

* BAT benefits from FDA ruling on Swedish Match

* Fresnillo slips after weak outlook (Adds news item, updates to closing prices)

By Muvija M and Shashwat Awasthi

Oct 23 (Reuters) - Shares in domestically-focused UK firms eased on Wednesday as votes in parliament kept investors guessing on the final timing and shape of Britain's withdrawal from the European Union, while the blue-chip FTSE 100 touched a near one-month high.

The FTSE 100 climbed 0.7%, hitting its highest since Sept. 25, as oil majors tracked gains in crude prices and miners benefited from a rise in nickel and copper prices.

The blue-chip bourse outperformed its European peers, aided by a rise in shares of BAT after the U.S. FDA authorized Swedish Match to market its snus product as less harmful compared with cigarettes.

The mid-cap index ended flat after spending most of the session in the red as uncertainty around Brexit and its consequences continues to show up in the performance of domestic companies.

Housebuilders, considered among the most vulnerable, were hit as Barratt, Persimmon and Berkeley shed around 2% each while UK-focussed RBS tumbled nearly 3%.

Britain's parliament accepted a Brexit withdrawal deal in principle on Tuesday but scuttled Prime Minister Boris Johnson's timetable to legislate on the agreement before a Oct. 31 deadline.

While lawmakers voted for a second hearing on the departure agreement, rejection of Johnson's timetable raises the likelihood of another delay in Britain's withdrawal as well as the prospect of a snap election before Christmas.

"The latest twist in the Brexit saga also means that investors may have to contend with more political risk by way of a UK election," said Han Tan, Market Analyst at FXTM.

Raymond James analyst Chris Bailey called the Brexit situation "a mess" overall and said the core scenario of an extension or an election was becoming more likely.

Precious metals miner Fresnillo gave up 1.7% after it forecast annual silver and gold production at the lower end of an already reduced target range, and reported a fall in quarterly output.

Centamin shone on the FTSE 250 with a 4.2% gain after its third-quarter production fell less than feared. (Reporting by Muvija M and Shashwat Awasthi in Bengaluru; Editing by Shounak Dasgupta, Patrick Graham and Alexandra Hudson)