Haha, that made me chuckle.
Thanks for the info Evol and Gradolabs, I presumed it would be fine to use ladybirds inside but just the novelty factor of having a mantis guarding my plants would have been awesome.
No matter though, a box of Ladybirds in the fridge it is, I refuse to suffer the pain of a spider mite infestation again.
Thanks again everyone.