It's a question of trade-offs. £350 extra, versus giving SAR a position accurate to 30m if you should end up in the water. Assuming the worst, if you lose your raft and end up in the water with only a lifejacket , the reduced time spent searching may end up saving your life.
Yes, that's the problem with all this survival gear. All you have to do is imagine yourself in the situation saying: "Damn, wish I'd spent that extra £350, then I wouldn't have to die!"
Hard to argue with really.
Thanks all,
QDM