Let me explain the problems with relying on that system in Uno by Uno basis:
1. If they use satellite for targetting then that means the defending force have to wait for the proper satellite in the right place above the enemy fleet, the problems is that GPS (or Beidou) are not real time & the enemy would have moved somewhere else. (Also the US can like shoot or sabotage the Chinese satellite if the conflict gets too hot. )
Real time data needed only in the final stage, when the missile/warhead is close enough to hit the target precisely and it is the function of the
onboard sensor. Thats why many missile especially the long range ones have
onboard sensors.
During initial phase, you dont need accurate real time data. Even inaccurate OTH radar will be enough to guide the missile approaching the CBG.
2. If it by air reconnaissance they have a choice between soft kill or hard kill. ( Jam or just blowing them out off existence. Considering it's the US or UK they will just choose the latter.
There is still OTH radars. How do you kill OTH radars located in deep enemy teritorry?
Besides killing satellites will be reciprocal, China could kill GPS satellite as much as US could kill Beidou.
3. Onboard GPS same problem. Unreliable data. It's basically no different than SCUD.
Which problem you mean, realtime data?
Nope! realtime data is problem for the distance sensor due to the travel time required by EM pulse. Again as explained above "
onboard sensor" is the key.
Otherwise, how come many missiles like sidewinder, amraam, meteor, pl-15 etc could hit supersonic target like jet fighter?
4. You forgot to mention is by submarine. This is the one that's more likely to produce result. But the problem is that a CBG would have placed Towed Array Sonar to protect the carrier group.
How submarine could guide the missile?
SBM real values are in force multiplier & as psy-ops. It's never meant to be useful against a CBG, against a single straggler ship it is useful. The problem is that it's almost never so.
If so then why US military view DF21/DF26 seriously.