My bed is under snow but will post some pics once thawed! As I'm on an allotment I didn't think my neighbours would welcome a 5ft hugelkultur casting shadow over their plot, so I dug a deep trench first (2ft or thereabouts) and filled this with old wood. This was the hardest part of construction believe me! Toby Hemenway in "Gaia's Garden" terms this a dead wood swale. Continued to build above ground so although my hugel is only 2.5 ft tall, it is actually 4 ft deep at least. Because I had to lay it running east to west, I hope this will also allow more light onto the north facing slope (Hope that makes sense).
As far as the acidity question goes, I reckon any decaying wood is going to up this so I don't think this will be a problem for the blueberry bushes. If anything, there is a risk of it romping too far into the acid range and I'm going to have to monitor this as the season progresses.
Citrus! You.re brave! I can confirm from personal experience that Japanese bitter orange is called this for a very good reason! I'm not going to tell you what to grow but there are always other options to explore. For me personally, citrus in the UK seems like high work input - low satisfaction output. Having said that, a few years ago I went to look at Geoff Hamilton's gardens at Barnsdale and remember he had both Clementines and Limes, outside, and fruiting well. He also had nectarines and peaches outside. I will have to go back and look at the siting and microclimates with new "permaculture" eyes.
Snow has stopped play here too, so I'll be back with pics of the site and Hugel once it's visible again.