Had another go at this as the previous ones lacked detail and was rather dark. so rendered out another using a HDRI image rather than corona sun, then combined it. really seeing the detail now on my scene. still not at all mastered this renderer yet and feel much more comfortable in Vray as I've been using it for years, it'll come though with more practice trying stuff out :)
the second image is the pure HDRI image with some contrast tweaks in PS.
Paul