It follows tabloid allegations the Chelsea footballer, 29, cheated on The X Factor judge with four women.
'In our opinion, it is a done deal and we are happy to hand over winnings now,' a spokesman for William Hill tells the Daily Mail.
Cheryl, 26, is due back in the UK from LA later this week.
In January 2008, single mum Aimee Walton claimed she had sex with Ashley in December 2007.
Last week, he was accused of cheating on Cheryl on two occasions in late 2008 with a secretary.
Now Ann Corbitt, 28, alleges she spent the night with Ashley in Seattle in July 2009.
And 29-year-old Alexandra Taylor, 29, claims she slept with him hours after he first went public about his relationship with Cheryl in 2004.
Ashley's solicitor says he has no comment to make.
Cheryl's rep has also declined to comment.
Where to next?
- Cheryl and Ashley's real relationship revealed
- What makes some men cheat?
- Latest celeb pics