my main medium in the raised beds i do is mushroom compost, i do add
any other organic material i may have around at the time but you could
add animal manures, or any other compost you can get hold of at the
time.

I've got some compost composting in my composter currently, so maybe if I
put all the autumn garden waste in it too, with a big dose of compost
accelerator, I can empty it into my new beds in the spring before the top
layer of soil.

Your mention of mushroom compost reminds me - I've got shaggy ink caps
coming up in one of my tyre pots I've got going at the minute. I believe
they're edible . . . hopefully they will persist once I've emptied the
compost into the base of my new beds.

Andy