Roger,
Many thanks, it's more a matter of me flailing around in unknown waters at the moment. If I can get used to LV and the viewfinder, I won't bother with the screen. I can't begin to tell you how much I miss my H4D viewfinder at the moment.
I should have hunted around here first instead of panicking and buying the screen. My R lenses are not fast. The 50 Cron and Zeiss 135 are my fastest. I will have the 28-90, 19, and 100 APO too, so speed is not brilliant.
It's good to hear that you can focus off the screen. I really need to go and practise and stop scaring myself on the net.
While hunting, I also found this
Kinotehnik - LCDVF Overview which was asked about here with no answers a while back. As a landscaper, this mightn't be a bad thing, but I'm going to go and practise.