Oh goodness, poor Purdey, and poor you
Why is you sleeping downstairs with her a problem? If she is crying non-stop for several hours, then she hasn't really learnt anything so far, and is probably very scared and stressed, which will make the next night more difficult for her, etc etc.
I really don't see a problem with you sleeping next to her crate for a few days; your presence will reassure her, and you can settle her with your voice before she begins to howl/cry and get worked up
After a few days, you can move to sleep further away - so she can hear, but not see you until eventually you can go back upstairs to bed
I then used an interactive baby monitor (still do), so that I can hear my dogs if they become restless and before they get so distressed that their noise wakes me upstairs
This will also help you understand the meaning behind her cries - she will need to toilet in the night, and her "I need a wee" cries will be different from her "I'm lonely" cries; this way, you can pop down and let her out for a wee when she asks, confident that you are teaching her something positive
I've not known this method to cause long term problems; the dog learns to sleep in their "usual spot" but with a bit of added reassurance until they have developed their confidence
Good luck