I have never been - you are obviously a fan and I can see why from your pictures - I particularly like the lonely Japanese Anemone against the brick wall. I do have a book of Christopher Lloyds' on the bookshelf 'The Adventurous Gardener'- unread as yet - maybe I should combine reading it with a visit to Gt. Dixter at the same time.
You are probably right about the slate chippings and gravel, they breed weeds.I should love to get to Great Dixter one day, I hope you enjoyed it.
What? I went to huge effort this summer to shovel 12 tonnes of gravel and now I come here and find it was not a Good Idea. How my heart slumps.
It was a good idea at first, but I took my eye off the thing and thought that violets and alchemilla mollis should be given free rein, not realising that they were sheltering less welcome plants, that I can't even name, and now my nails are shredded and my back is sore with trying to bring it back into order. Also 12 tonnes sounds like a much more weed defeating amount and you are younger than me and more vigilant I am sure. You also have more daylight time for dealing with it all.
Lava rock also sucks. Sorry for the bad language, but we are fighting a losing battle with creeping, spreading, nasty fingered weeds.