Thought I'd post a review of Autosmart's G101 APC (All purpose cleaner) for you guys.
G101 APC
I recently done a Porsche carerra 4 and here's some pics of the rear arch lining (Engine located next to it, so it was rather grubby).
For this, I used the G101 diluted at 8/1, which is pretty weak. Because I used it so weak and had a tin of Gunk (In aerosol form) to hand- I sprayed a bit of that on the stubborn areas, but most was done with just G101.
Before pics:
Spray on:
Agitate with a nail brush or whatever brush you've got (Wouldn't recommend a wire brush or hairbrush through

):
Hose/ Jetwash off:
I actually repeated the process again after hosing off as I missed a couple of bits.
TBH I think if I diluted it to about 5/1 I wouldn't have even needed the gunk on the more stubborn patches.
I'll update this thread next time I use it.
So far though, I rate this product 10/10! It goes a very long way, you can use it with very minimal effort, smells quite nice, and diluted properly, can be used on near enough anything. Great for carpets/ mats etc!