** Shares of British financial services provider Alpha Group International ALPH.L jump as much as 7.7% to an all-time high of 3,025 pence
** Co says it has rejected an all-cash proposal from U.S.-based business payments firm Corpay CPAY.N
** Co did not disclose a reason for turning down the offer
** Under UK takeover rules, Corpay has until May 30 to make a formal bid or withdraw; deadline may be extended with UK Takeover Panel approval
** Stock up 29.3% so far this year
(Reporting by Amna Mariyam in Bengaluru)
((amna.mariyam@thomsonreuters.com))