DIY potting compost

Forgot to add, the reason for not putting more home made compost in my recipe is because it shrinks too much. You end up with a gap down the side between the potting mix and the pot wall, and when you water it all goes down that gap and straight out the bottom. To avoid the mixture becoming too compact and hard to keep wet you, need something in there that is more resistant to degradation. That's one reason why peat is such a good growing medium: it's very chemically stable. The coir, bark, wood fibre and woody bits in peat-free compost do a similar job.