* William Hill, GVC conditionally agree reduced price
* 56.1 p/shr bid would value Sportingbet around 485 mln stg
* Deadline for formal bid extended to Dec 18
LONDON, Dec 4 (Reuters) - Britain's biggest bookmaker William Hill and partner GVC provisionally agreed a deal to buy Sportingbet, cutting the proposed price after the online gaming firm's revenues slipped.
William Hill said in a statement on Tuesday that it had agreed a cash-and-shares proposal worth 56.1 pence per Sportingbet share, valuing the company at around 485 million pounds ($781 million).
The bidders had originally proposed 52.5 pence per share, rejected by Sportingbet. That was sweetened in October to 61.1 pence, which was more palatable to the Sportingbet board.
However, the online gambling company said last week that first-quarter revenue had fallen 35 percent after a quiet spell in the sporting calendar, leading to speculation that William Hill might seek a lower price.
Sportingbet said it would recommend the revised 56.1 pence price if a formal bid was submitted. The deadline for a formal announcement was extended from Tuesday to December 18.
Sportingbet shares closed on Tuesday at 45.6 pence, indicating uncertainty as to whether a bid would materialise.
William Hill, keen to expand overseas, wants to take over Sportingbet's Australian business and may also be interested in its Spanish operations.
GVC would take on other units that operate in countries where the regulations on gambling are less well defined and the risks consequently higher.