Outlaw, Thankyou for your efforts with this, its much appreciated!! 
I recently bought the Halfords turbo, with speed/cadence sensor. I run very basic figures on cadence/speed same gear ratio, low wind, flat road etc. I found resistance 4 to be as close as I could get. Now a few months on Resistance 4 I’m completing a lap of Watopia with avg 295watts. That seems high to me, iv switched to resistance 5 now and I’m avg 235. After getting annoyed maxing out 400watts sprints with unlisted trainer, iv changed to TT-01 trainer still on resistance 5 and I’m avg 250watts.
What I’m after establishing is, am I way over with my FTP still? The reason I suspect this may be the case is my Strava Avg ride is usually between 150-170watts, where my HR is usually higher. (I know not the most accurate comparison to have!). Just after some pointers to get as close as possible so I can start to enter races without smoking people who are probably miles fitter than I am, thus annoying the zwift community 