Andy, TBH if i wanted a FF i would go 5DIII everyday over the 6DII, it seems from what i have seen the 6DII is basically an 80D with a FF sensor, in your position i would get the 80D.
As you have a nifty 50 and a super wide angle zoom do you really need an 18-55? how about a 1.4x extender III...