Bog Standard?

I can think of a few:

Requires less force to flush, you can have an internal overflow, simpler mechanism that does not tend to suffer from loss of performance as the paddle wears.

There is little danger of a syphon leaking into the pan incessantly.

You can do this with them

Looks impressive, and the website looks good.

Any idea how the epoxy is standing up to constant immersion?

The message from "The Medway Handyman" contains these words:

Can replace moving/sealing parts without dismantling close-coupled toilet. A lot better than the dreadful American versions of the same thing, though.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember YAPH saying something like:

Excellent idea. I have one of those available to me to replace one that was nicked from my building before I took possession.

They'll keep you in work if you only offer 12 month warranty. They leak after not much more than a year.

I haven't been back to the customer since so I don't know either way of any problems, but having used Araldite in various applications over the years I've not found it to be bothered by cold water.

TBH I'm not enamoured of either flap or drop valves. At least the flap valves are simple - drop valves seem a nightmare of complexity which is asking for trouble. Polythene-diaphragm syphons are clunky but at least they're inherently leak free. However what's wrong with the ancient bell syphon? I've been mentally doodling designs for an updated version using plastic components, with power assistance derived from the incoming water supply. Not quite ready for dragons' den yet though :-(