You're quite right of course. I think they've got the right guys in their crosshairs. One of them at least is certainly a nasty piece of work.
I don't think they'll find her at Coombe Abbey. Maybe she'd been taken there initially, but the place is overrun with dog walkers, and dogs are notorious for finding bits of people.
I know Coombe like the back of my hand as I grew up within cycling/walking range. There's a back entrance, but you have to use right of way access through a busy farm property after crossing a bridge over the M6, and I'm sure they wouldn't get through that at night without raising suspicion. It is a very quiet area of the park though.
There used to be a horrible patch of scrub between the Asda at Walsgrave Triangle and Coombe, and also a fairly extensive wildish area where the Sowe "river" meanders past the Walsgrave Hospital up towards Clifford Bridge Road. These two places are much less frequented by people but the latter area behind the hospital does have dog walkers. Both of these sites aren't too far away from where she was last seen, either.
Farmland seems like ideal places to hide people to me - it brings to mind Fred West's first victim (frantically googles) Anne McFall who wasn't discovered for nearly thirty years.