I got 2 x 500ml bottles of Sonax from my local Vauxhall dealer - "old shape" so they let me have em for something like £2.50 each. Nice stuff and sheets well, too. Gave my dad some for his new motor.
Managed to get R2000 at same dealer - was part of a wheel care pack which they kindly split for me. I was surprised not to like it as I'd read David's review.
I had a Laguna with the 17" multi-spoke wheels and it was filthy (was supposed to be a replacement for mine - long story!) with ingrained brake dust and muck. Sprayed the R2000 on, left for 5 minutes, agitated with my wheel brush, left for a further 5 then rinsed. Cleaned the loose dirt well but didn't shift the baked on stuff - so IMO performs as well as APC+ for me.
Alex suggested giving the P21S gel a try which I might do but for now will stick with the APC+ - did GF's Ka yesteryady and last time that was washed was 4 weeks ago. Wheels came up sparkling after simple cleaning with the APC+
I've been told that Halfords ask for £250k in marketing & product up front with no guarantee that they will actually stock the product and they have 180 day payment terms. That came from another car care supplier so not sure whether it's 110% correct or not.