Be on the look out for any rip off VM pricing if you call them. As your cat damaged the PSU, VM can reasonably expect you to pay for a replacement. But I'd not be willing to pay more than £20 for a VM official PSU, as there's nothing special about it. My Hub 3 was supplied by VM with a Liteon PE1300 9AR5 psu, so not even made by the supplier of the Hub 3 itself.
Personally I'd be entirely happy with any good quality 12V 2.5A PSU, and you could buy (for example) the Myvolts branded "brick" that costs £13.99 on Amazon and comes with a 10 year warranty, or if you search Ebay for Liteon PE1300 9AR5 you'll pull up the exact Liteon model including unused ones for £10-15.