1) Did you call it the St Giles Hospital for a reason? Is it related to the Fellowship of St Giles and the Red Court?
Not intentionally no, but that does leave it open to have some connection there - perhaps a good way to get the PC's involved? The Hospitals Administrator might be able to call on a favour from the White Council to get them involved and without a Warden available they get the PC's to check it out? Although the name in itself might make it an obvious target for the Red Court?
2) ...The sorcerer might well be chopping off limbs to fuel his dark magic, however he might not be the one animating them. Perhaps one of his previous victims is in a coma but his latent magic is animating arms and legs, both prosthetic and dead, in a desperate attempt to 'wave' for help and take revenge.
That way they've got the typical bad guy to kill, but they've also got a bit of a puzzle to solve and a moral quandry too; the comatose patient is a danger to those around him (perhaps a doctor is strangled to death by accident during the chronicle) but it's not a conscious choice of his. A ward would contain his power for a while but it will easily be broken by the doctors and nurses as they care for him. Can they afford to leave him alive? Can they communicate with him somehow? etc etc.
Hope that helps 
I like this, it fits in very well with the AAAA's idea from the "Our World" book and gives an additional layer to the story.
Have the Sorcerer be what appears to be the main threat, a surgeon who works at the hospital who has been harvesting limbs - initially with the idea of creating prosthetic limbs for patients that "feel" like their old limbs (because essentially they are the old limbs?). Where he went wrong... perhaps he started amputating patients who didn't need amputation so he could refine the process/ritual and therefore maybe planted suggestions in patients heads to enable him to get away with it? When they find/defeat him, they discover that he wasn't directly connected to the murders.
Perhaps by looking at his recent patient list (?) they find that someone he operated on is in a coma and like you said is animating limbs to cry for help (or could this latent ability be creating ectoplasmic limbs)? Maybe during the investigation they discover this particular patient came around during the operation and was in a semi-concious state. He could be eliminating those that he saw thereby exacting his revenge?
The plot thickens!
