PARTNERSHIP UPS HBO <HBOC.O> STAKE TO 8.7 PCT Andover Group, a Great Falls, Va., investment partnership that is seeking control of HBO and Co, said it raised its stake in the company to 2,026,000 shares, or 8.7 pct of the total, from 1,626,000 shares, or 7.0 pct. In a filing with the Securities and Exchange Commission, the partnership said it bought 400,000 HBO common shares for 5.4 mln dlrs on May 28. The group, which has a slate of candidates seeking board seats, said it would decide whether to submit an offer to acquire the company after the HBO annual shareholders meeting, which was to have been April 30, but was postponed.