As I understand it, if one or more clubs are to be relegated for ground grading, then a promoted club which hadn't met the deadline to upgrade their facilities would be relegated first, even if they were no the lowest placed club who didn't have the grading.
That's my understanding as well. In the CCL, Farnham have until March 31st this year to get an 'F'. They haven't got much to do but, if they don't do it, I think they're going down before anyone else is considered. All the other teams in the division already have an 'F' or higher according to the league.
In CCL1 the FA have given clubs until 31st March 2013 to get a 'G' before they face relegation. I don't know if they'll be relegated en masse after that or whether they'll only go down if the division is full and there are teams coming up to replace them.
The Kent Invicta League has four more years to get its clubs up to the required standard I believe.