Yes ive just read that Dave .... And ....
Where's it say GG4 
On my kids lives ive never used or seen it . 
Again I'm baffled . 
Ecover was very goid , but come summer and impossible to judge how much was in the tank it was proved to be very poor in hot weather and if a build up in your tank was poor . 
Vision has overcome that above point . 
It's good that you've come across GG4 , but don't mis- quote me as it's unfair . 
I'm pleased for you Dave Willis if this works for you , I won't be saying anything negative as ive simply never used or tried it