It is very difficult to find information on the details in the garden.  However, here is a little bit of the history of the Pagoda Fountain:

The pagoda was intended to be eighty-eight feet high. It is placed on an island, in the centre of a small pond, and was to have been approached by a Chinese bridge richly ornamented. The diameter of the base of the pagoda is forty feet, and there were to have been six stories, the lower one of stone, and the others of cast iron. From the angles were to have been suspended forty highly enriched Chinese lamps, and these were to be lighted by a gasometer fixed in the lower story. Besides the lamps, there were to have been grotesque figures of monsters projecting over the angles of the canopies, which were to spout water from their eyes, nostrils, fins, tails, &c.; a column of water was also to have been projected perpendicularly from the terminating ornament, on the summit of the structure, which, from the loftiness of the source of supply, would have risen to the height of seventy or eighty feet.

However, the eventual design and build was by Robert Abraham, and was made by the Coalbrookdale Company, which, at this time had moved into the construction of ornamental iron works. It would eventually have, not the six storeys envisaged by Loudon, but three, and have ornamental bells suspended from its roofs, instead of lanterns. Its most impressive feature would become its fountain, which is still maintained, and delights visitors today.

PS: I just updated this post 02/11/11 22.20. A couple of the photos had disappeared….