Hugelkutur? (@ Taff, or anybody else who knows what it is)

depends if it'll work in your area ........
Hugelkultur: Using Woody Waste in Composting

I'm going to make one, and also, I have one bed of very fine earth that dries out badly because next door has let a self-seeded buddleia take over, it's taking what little moisture was left, so I'm going to get the earth out, then put a modified version of it in, logs underneath, then fill again with the earth and a bit more stuff.
From reading lots, it's good for areas that are dry all the time, whether that's in your garden or elsewhere.
The logs, rotting or green act as a storage unit for water, so you don't have to water much or at all, depending on the age of the logs and the decomposition.
Also perfect for making higher than normal raised beds, don't be afraid to put huge logs into it.
Also, the first year, the decomp is obviosuly going to be less than folowing years, so potatoes are recommended for it, or something like that.
I've read a lot about concerns of the logs robbing any nitrogen, but you alleviate this by putting in what americans call slash. which is basically just your weeds cut down. You could also plant your mulch into these beds, like comfrey or nettles, or a nitrogen fixing cover, like clover etc.
There are loads of interpretations of what you can grow on them.
For further reading, I'd recommend Sepp Holzer, or Paul Wheaton, also vids on You Tube.
raised garden beds: hugelkultur instead of irrigation

actually, any wood, rotting or otherwise, will do, logs, planks, wood chip etc. It should be in contact with the earth, and then it'll do it's thing

this thread will give you most of your answers, plus pictures of beds in action and being made, although they are american-size for the most part.
One plus of building them here is that we do have a lot fo rain [for the most part] so if you have boggy areas, the beds should shoak up the water in those places too.

http://www.permies.com/bb/index.php?topic=17.0

Thanks, at first glance it looks an interesting way of using woody waste that could otherwise end up either being burnt, taken to the dump or piled in the corner of the garden.

It'll take ages to read that thread, can't do it at the moment, so - if we were to, say, try to bury stuff that won't go through a shredder, about how deep into the ground would it need to be so the soil could be used for crops?

I think it's probably a dim question and the answer's probably obvious, but I don't seem to have my thinking head on at the moment.

Either dig a shallow trench and fill with the woody stuff, followed by any turf from the trench on top, weed cuttings, leaves, manure or compost, then a layer of soil, or lay the wood straight onto the soil and build up from there.

Go to the link I posted first for an idea of the shape of the bed, there are pictures down the right hand side. It's only one page.
it can be used for crops straightaway if you want, but the soil will settle, so you will have to top up by next spring. The plus is that the bed wil be warmer, like a heated compost heap thanks to the decomposition, so you can use it earlier than other beds.

No idea how burying it completely would work, I'd imagine it would have to be in good soil, otherwise subsoil won't give it the means or the bacteria/fungi to start off decompositon.

I haven't ignored your reply, honestly I haven't - I've been dipping into the other sites as and when I've had spare time, to find out more about this idea.

It's an interesting concept, but not many people have access to huge lumps of wood that would take tens of years to rot down, so would have to try to make do with much smaller stuff.

don't worry, I was sending my typing into the ether, not expecting a huge discussion, I'm just all excited by the idea.
I haven't got huge lumps of wood either, I have a lot of wombled scaffold planks, and other bits and pieces, including some wombled tree chippings, so I'll be using those
When I get my rear in gear, I'll post pictures