The FCA and European Securities and Markets Authority have pretty comprehensive resources dedicated to the regulation around short selling, links below. Of particular use, are the disclosed short positions, which are updated daily.
FCA’s short positions list:
FCA Disclosed Short Positions Daily Update (xls)
ESMA have a list of lists:
ESMA Net Short Disclosure Lists (pdf)
The links are prone to breaking, so feel free to update them as they change. I will do my best to keep on top of it. Also, make sure any links point to legitimate market and/or regulatory authority websites.