Thank you all for your kind comments.
PrzemoL: I ran out of time to do the double flying wires before my club competition - now the motivation is not so strong to do more rigging. I did bother to put in the fuel lines from the fuselage up to the gravity tank but I didn't feel the need to build more details. I also didn't scratch build a bomb sight for mounting in front of the front gunner's position nor the metal loop thingey under the sternpost that was used when hauling the aeroplane out of the water, nor the rope that would have been tied to the fitting under the hull and a cleat on the fuselage side. Everyone has to decide how detail-afflicted they want to be!
Water Effects
I started with an 8x10 wooden photo frame and glued the wooden board inside the frame. Next I bought an aluminium foil oven liner (which is quite a bit thicker and more durable than kitchen foil) and proceeded to burnish out all the moulded patterns until it was a flat sheet. Crinkle it up a little bit depending on how big you want the waves.
Spray paint the foil your desired sea colour - I would suggest a dark grey/blue or dark green (but I found it had to be sufficiently different to the plane wing colour). When dry, cut the foil to fit tightly inside the wooden frame. Measure twice, cut once! My first one was cut too small

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For the Felixstowe I worked out where I wanted the plane to be positioned on the base then cut the foil from the edge in a straight line up to the desired point. Next I cut a notch at the end of the cut that was big enough to take the thickness of the brass stand I had glued to the plane. Slide the model along the cut so that the foil is in between the hull and the bottom of the brass stand, and glue the plane to the foil using CA. (this took 2 people/ 3 hands) Next I glued another piece of foil under the long cut so that the sea would be reasonably even - but don't worry too much about this because the plane's wake will cover the cut eventually.
Now glue the foil and the plane's stand to the wooden frame - I used liberal amounts of 5 minute epoxy (and again 3 hands). Now for the seawater! I used Mod Podge for the seawater.
Mod Podge, Glue & Decoupage Products from Plaid Enterprises
It is an acrylic medium that looks like white PVA wood glue when it comes out of the bottle, but dries (eventually) clear and hard. You can buy it in art/craft stores and is used for decoupage projects. Pour lots onto the foil and use a large paint brush to push it around until you have all the foil covered. Watch out for tiny air bubbles which may form, and pop them with a needle before the Mod Podge sets. I wouldn't shake the bottle before starting as this may cause the air bubbles. A second coat is a good idea to build depth and even out the surface to some extent.
The wake is made from a kitchen cleaning pad that comes in two layers - a foam pad with a white scouring layer. Peel off the foam layer and then cut up the white scouring bit into smallish bits. Tease the small bits out using fingers or tweezers then place them in the wake in the wet Mod Podge. Build up the wake with more pieces until it is high enough for the effect you want. Final step is to paint the wake with a little more Mod Podge to give it a glossy wet look.
To be honest, the sea and wake look better in the photos than the model does 'in the flesh', as is the case with my other seascape dioramas (although I haven't photo-shopped the pics at all). This is partly because I hold the model up to the light when photographing it to maximise the reflections.
I like the idea of seaplanes in their natural environment - they look so much more attractive than having the plane up on a beaching trolley.
Happy Modelling!