I lived in England for about a year in the late eighties. As I recall, the Brits pronounced it, 'Jag-you-are'.
I live in Dallas now. The natives here pronounce it, "Jag-wire'.
Either way, it sounds strange to my California bred ears. Out there, we pronounce it, 'Jag-warr'.
Actually, it’s a pretty cool word in that way. Of course in my midwest, Detroit accent I pronounce it as Jag-U-uar or jag-u-wire.