Be guided by the natural seeding. Aqualegias cast their seeds as soon as they were ripe after flowering.
And make sure the water butts are completely covered.
When you said very large I thought you meant very large. At 7 foot high it's still a young plant. They grow much, much bigger than that. Make your decision soon because they grow fast if allowed to.
Peace Lilies like a subdued light position. They hate the sun.
Yes, they are lovely, but........they are ripped out of their native home, transported half way across the world, just to die in the UK from wet and cold. They are much prettier growing in their native habitat.
Do not feed them or you will encourage them. As to the pond; they are doing what foxes do. Looking for food.
Sounds like they are hungry. If you leave them to grow on, likely they will bolt.
Take three apples plus a shoot of the tree to an 'Apple Day'. They are held all over the country at this time of the year. But be quick or you'll miss them until next year. They look pretty distinctive; there will be an expert there.
IMO palms and especially tree ferns always look alien and out of place in UK gardens. What about native trees which do not need such care?
If it has seeds, it must have had flowers. Perhaps they were insignificant and you missed them.