That's an incredibly helpful response - thanks @Carlston
Yeah like James I don't really want to change my rims at this stage, however do need new tyres which is why I'm looking into all of this... I'm after some 4 season tyres as am often driving in rough, wet and muddy conditions... and I have to say as much as i love the ride and style of the Yeti I've always felt the tyres look a little weedy in those big arches!
Going with 215/60 R17 as James did seems like a good option however I've noticed that the tyres I'm after - Bridgestone Weather Control a005 - also come in 225/55 R17 which seems like an interesting option? I've used a tyre calculator and this would have a more subtle change - closing the arch gap and raising the ride height by 11mm and only altering the gearing by 3% or so.