Compost for azaleas

[Thinkle]

Having successfully killed a young Rhododendron i have done some retrospective research and discovered by neutral PH soil and south facing border was a match made in hell for the poor thing.
I am however (for sentimental reasons) still quite keen for a plant from that family so my next plan is a potted dwarf azalea. I’ve found one that can tolerate some sun and be grown in containers, so I’m onto compost... I need some ericaceous compost and that is on my “bag” but I’m loathed to spend even more money on some John Innes No3 that they also recommend. I have some spare Carrs Organic Soul Improver from my roses. Can I use this? I think I also have an unopened bag of general purpose compost in the shed but I need to check.
Also, is it a terrible time of year to plant these? I’d like them to be in for the spring flowers

You need ericaceous compost for azaleas.

Sorry I didn’t explain well. The online nursery recommends mixing the ericaceous compost with something like John Innes 3, can I sub the latter with my Carr’s soil improver?

You could just use the ericaceous compost on its own. You need to avoid anything with lime in. Carrs soil improver, according to the website is composted manure, straw and bark, and is pH neutral, so should be OK. It's not going to appreciably raise the pH of the ericaceous compost.

JI no3 is a mix of soil, peat and nutrients, so the Carrs wouldn't be a direct sub for this.

I too don't like buying dozens of different composts. So in your situation, I'd use ericaceous compost, but bulk it out with the Carrs if I was short (ie if I needed 1.25 bags, I'd buy one and bulk out).

Thank you, that really is very helpful.