CCF= Closed Cell Foam. Its blown foam that doesn't soak up water, as opposed to OCF Open Cell Foam like a washing sponge. R value; yep, the higher the value the warmer
Getting out and testing your gear is the only way to know, we can all offer guidance only as different people sleep at different temps. Also, the combined warmth of sleeping bags needs to be tested as its just as much a matter of how well they 'Nest' than thickness of insulation-Its easy to compress insulation to the point of vastly reducing its loft.
On paper, I would sleep out in that setup in most UK conditions.
Getting out and testing your gear is the only way to know, we can all offer guidance only as different people sleep at different temps. Also, the combined warmth of sleeping bags needs to be tested as its just as much a matter of how well they 'Nest' than thickness of insulation-Its easy to compress insulation to the point of vastly reducing its loft.
On paper, I would sleep out in that setup in most UK conditions.