Indeed, theoretically you probably don't "need" an IR to fly a Kingair on a purely being legal basis. However, a quick google finds all the TRTO's wanting an IR as a course entry requirement.
To operate a Kingair sensibly, not having to stay VFR everywhere, (although if you're in a part of Europe with reliable nice weather it might work), you're really going to want an IR.
In the UK, you might just get away with an IMCr, depending on which airfields and routes you wanted to use.