Hello Jonathan, It's very hard to say what is in a bag of organic compost/conditioner, if as now you spread it on the top of your garden in the summer heat it will be reduced to a very small amount in days with all the nutrient oxidised quickly. Dug in deeply it may hold some of it's value. Having made tons of compost, leafmould etc. over many years a bulk of whatever you are using will make a vast improvement. One 60litre bag purchased will only cover one or two square metres.

This is what they say J - 'Levington Organic Blend Soil Conditioner is a perfect blend of 100% peat free composted materials, which improve soil structure and drainage of clay or sandy soil. Aids plant establishment. Improves drainage and suppresses weeds'.
I use soil conditioners (not organic) to help my clay soil, just because I cannot make enough of my own compost.

So am I to mostly think of it as humus rather than as nurtient rich substance, other than as when I am using it as mulch only? Yes, I have found that one bag does not go very far, but I only have a very tiny garden, so just a few more bags should do my entire area.

Thats how I see it J

Near to all of us is somewhere we can purchase good soil conditioners. Many times I see good soil in skips being taken away for landfill. There is an alternative at your local allotment association which gives good discounts on all garden products. A conditioner is usually humus with added grit for drainage but will vary bag for bag on your different purchases. The only way for a small garden is to do as you are now.

Yes the grit part of it helps in my clay soil DB

Thank you all.