I’d be almost certain that Secret Squirrel was only entered as a fall back in case Wincanton was called off.
As for the rest, there are several that have zero chance of collecting any prize money, so the £40k shouldn’t influence their decision. For example, Tide Lines is a 5-y-old mare that would be making her racecourse debut. She clearly isn’t going to be competitive, so why run her in a maximum field containing 80+ rated opponents?
Experience says that the usual take up at the final decs stage is around 50% of those entered. I agree that might be higher here because of the prize money. And some of those almost certain to be eliminated may declare to get a refund of their entry fee.
I stand to be proved wrong. nobody gets these things right 100% of the time, but I’ll predict that CH will end up as No 12 on the racecard.