Thank you I will have a go now with a little more confidence than I had before, it makes sense to me now you mentioned all the plants sharing root ball as I have a plant with lovely yellow flowers ( lost the card so dont know the name ) it grows quite tall & was in a small basket on the shelf at the front of the pond but this year it came up at the other side as well been newbie to ponds I couldn't work out how it got there problem solved. I suppose this happens with most first timers but I find my pond too small now & wish I had dug a larger one & designed it myself we had the little plastic pond given & I was hapoy with it the first year but now would like bigger but too worried of disturbing & losing the frogs & any thing else in there.
Yes, a bigger pond would mean not having to be so wary of the spread of plants. I've got a medium sized pond with water forget-me-nots and also love their beautiful little blue flowers, but do end up having to be quite brutal with them every few years. For smaller ponds the cull might have to take place every year.
Having said that, your pond seems big enough for most wildlife. Some dragonflies and amphibians (eg GCNs) like bigger ponds, but most pond critters are quite happy with a small pond.
The yellow flowers....Marsh Marigolds perhaps?