07 reg octy scout off-road tyre setup

Need advice on getting all terrain tyres fitted on my scout currently have the stock scout 17" alloys with 225/50 R17 summer tyres but do alot more responding as a medic at events so want all terrain tyres like the look of geolanders but what size wheels are best to best size tyre as my local skoda dealer is useless and i no its possible as skoda did it back in 2007/2008 3000 mile trip across middle east in stock scouts to prove how bloody good they are. 

Please can anyone help