Thunder 119 for 3 (Heap 46) beat Sunrisers 116 for 8 (Griffith 36, Cross 2-20, Lamb 2-24) by seven wickets
All three are in contention to play in this summer's home Ashes from next month and shared five wickets to limit Sunrisers to 116 for 8 having elected to bat, laying the platform for a seven-wicket win with 21 balls remaining.
They were miserly with either seam or spin, with Cross's 2 for 20 from four overs of seam the most encouraging having battled against a tropical disease in recent weeks. Ecclestone struck once with her left-arm spin and Lamb twice with her offspin.
This was Thunder's first victory in eight 50-over and T20 matches in 2023, including back-to-back defeats at the start of the Charlotte Edwards Cup. For Sunrisers, they have now played three and lost three in this competition.
Cross, who recently revealed that she had to go through nine courses of antibiotics to treat an illness picked up abroad in pre-season, set the tone with the second ball of only her fifth match of the season.
She uprooted the off stump of former South Africa international Dane van Niekerk for nought, a peach of an away-swinger leaving Sunrisers at 0 for 1.
Crucially, only one other batter, Flo Miller from No. 7, reached 20. She was bowled by former team-mate Naomi Dattani in the final over an innings which saw Thunder captain Ellie Threlkeld chop and change through seven different bowlers to deny Sunrisers any rhythm on the same pitch used for Thursday's T20 double-header day.
While Lamb returned 2 for 24 from her four overs, Ecclestone was the most economical bowler on show with 21for 14 from her four.
Her wicket of Amara Carr caught at mid-off following a miscue was sandwiched in between the two Lamb strikes as Sunrisers slumped to 81 for 6 in the 15th over. Lamb had Grace Scrivens caught at cover and bowled Jo Gardner.
Lamb later gave Thunder the ideal start to what proved a serene chase, clipping a boundary through midwicket as 10 came from Kate Coppack's first over.
Both openers played their shots, and Heap made the most of being dropped on 16. Thunder reached 50 without loss after seven overs, by which time the game was only going one way.
Heap maintained pace with her more experienced partner and overtook her after Lamb had been trapped lbw sweeping at captain Kelly Castle's offspin - leaving Thunder 64 for 1 in the 10th over.
Morris flicked the offspin of Mady Villiers to short fine leg shortly afterwards, leaving the score at 74 for 2 in the 11th, but Heap gained support from West Indian overseas Deandra Dottin to get their side over the line.
Unbeaten Dottin crashed two big straight sixes in 26 off 15 balls, while Heap was bowled by Eva Gray just shy of 50 with only 10 to win.