Has anyone fitted the e3d v6 to a prusa i3? If so how did you go about it?

That is the default hot end for the current model that Josef Prusa is selling now, so parts for mounting it should be available for download on his website or github.

what hotend are you using now? there is a chance that the e3d hotend is compatible with the hotend mount you have right now.

if so, just remove your current hotend, install the e3d and connect the wirings.