Next time, Sem, add your extra comments under your original question please - saves us having to click on your avatar, go to your profile page, select your previoius question and re read it, then back to your profile, back to the questions page.
I'm wondering who told you you need ericaceous compost for these - it's certainly not a piece of information I've seen anywhere at all - they like nutrient and humus rich soils, but will tolerate most conditions other than heavy clay, which isn't a problem in pots.