We have had the girls for two weeks now, and have a better idea of their temperaments and issues.
Physically they are doing brilliantly, raw certainly agrees with them, and they are both happily using pee pads.
Mouse is halfway through her season, and is taking it all in her stride. She flirts shamelessly with Harley though, poor boy! Her marking has reduced, as she gets more settled and her hormones level out I don't think it will be an issue. She is doing really well outside, she is anxious when there are other dogs and people around, but behaves well. She will give a little warning growl if a dog is being too full-on, but is quite submissive. She will allow people to interact with her, but isn't comfortable about it. I think once her season is over she will be fine, I am just introducing her to more experiences gradually. Her only other unwanted behaviour is that she wants to lap-guard, but she understands now that this means the end of lap privileges. She is very easy to train.

Delilah is a different story altogether! In the house she is happy, bouncy, and quite rambunctious. A happy little girl. Outside, she is terrified. She gets hysterical when she sees another dog, snapping, snarling, and screaming even when the dog isn't close. (Even a whole field away) She is scared of people too, but gives a warning growl before she snaps.
She is much more dependent on Mouse than Mouse is on her.
On the plus side, she is better with the unfamiliar outdoors now, leaves and sticks no longer terrify her. She also comes straight back to me if she is unsure, she definitely trusts me now, and will happily follow me even in places she has never been before.
Any advice on ways to help overcome Delilahs issues will be much appreciated.