Re a uk wild life pond.
Mine has a very shallow outer shelf, say 3" to the liner with garden soil on top of the liner, in places this breaks the surface.. The remaining shelves vary between 6 and 9 inches to the liner, again these are covered with loose soil. If possible use a grass verge and as little as possible freeboard liner showing above the waterline, this is to make animal access and ESCAPE as easy as possible
Most of the plants grow potless, with the current exception of bur reed. However it looks like I will have to lift typha latfolia and pot that in a solid container to contain the root system. I have another unknown reed like plant that may also need potting.
If you go with loose soil be prepared for a huge crop of blanket weed in year 1 before the higher plants become established, by the end of year 1 or by year 2 the BW will most likely be gone. Possibly due to nutrients being locked up in the nitrogen cycle. DO NOT feed the fish which should be native, eg stickle backs and or minnow and DO NOT add gold fish.
The deep of my pond is 18", I hit a layer of compacted stone dust which I would have needed a jack hammer to get through so thats as deep as it got.

Plants marsh marigold, Caltha palustris for early colour.
Bog bean a very delicate little flower, marsh pennywort but you may need to control the spread of that, brooklime but plant that where it has to grow upwards rather than allowing it to grow outwards it looks better going upwards
ivy leaved crowfoot nice white flower but that is easily overrun, likewise golden buttons
mints,
water celery or parsely I can never remember which but that spreads like wildfire.
water starworts, water violet, DO NOT get tilea recurva
frog bit, water soldiers, bladderwort,
greater and lesser spearworts, large and small plantains, common rush and the larger types, some of which are variagated,
iris, mainly yellow flag but they may need potting too
water hawthorn and maybe lilies but take care that lilies are not crowed by oxygenators etc as they dont like the competition for light.
Oxygenators, elodea crispa = lagarosiphon, milfoils, water buttercup =ranunculus aquatilis??, hornwort, DO NOT get elodea canadensis.
cotton grass
loosestrife but deadhead that and it may need potting

Azolla has not survived in my wildlife pond since the end of year 1, even if accidentally added, which is a blessing, I suspect it is out competed for nutrients by native plants.
This is my pond, of course so densely planted is not to everyones taste but the wildlife seems to like it, big fish would struggle in my pond. There were some goldfish in there that got in as eggs on plants but even a 3"er had to fight its way through the vegitation in some places. The water goes all the way to the left of the photo and to the edge of the dark along the top, the clearish bit in the foreground is the 18" deep, there is no filter but there is an aquamax 5500 circulating water through an internal stream around a bog in the upper left corner
http://i8.photobucket.com/albums/a9/...ldlifepond.jpg