"I don't know if Apple are already paying FRAND for these Samsung patents but lets assume they are not."
Let's assume they are because if they were not they would have got sued by every other phone maker the moment they released the iPhone and on 3G, the iPhone 3G. Also with FRAND licenses there is no "wiggle room", it's a "take it or leave it" proposition. One of the point's of FRAND is that if you pay the fee you don't get sued later, they are structured so that you know you are OK. If they weren't they would be worthless, there is no point in paying for a license where you can still get sued later because of "wiggle room". FRAND licenses are like motorway toll booths, you pay the fee and you can drive down the road, you don't won't to pay then fine find your own way, take a back route but don't ever put a wheel on our tarmac.
We have seen this before, Rambus tried to abuse a FRAND (OK more complex than this case) license and got it's arse handed to it, after about 8 years of litigation. Nokia tried to do what Samsung is doing with Apple but settled. In the Nokia vs Apple case Nokia was in an "almost can't lose position" because Apple agreed from the start that it was using Nokia IP and had to pay Nokia but said Nokia's IP was licensed under FRAND and so all Apple had to do was pay the same fee that everyone else was paying.
Apple won, well the outside lawyers won but it is clear from the settlement that Apple just paid the FRAND (maybe with interest) license. This is a PR job by Samsung and not for the tech heads and tech bloggers who don't matter but for the courts who do. It's also a sign of desperation as Samsung must know that if this ever gets to trial they will lose.
One final thought for anyone who thinks this is anything beyond PR and tactics, Samsung are the second biggest maker of smartphones and feature phones (Apple and Nokia are #1 respectivly as of Q2) and the largest LCD and memory manufacture in the world. All of those are produced under FRAND licenses!