I think your idea of a constant drip may be different to mine. Any maybe better. But it seems more complicated.
Over the next days or so, I might post some pictures of how I do it.
Midwater thank you, that would be really helpful, in return I'll get this sketch done to scale and maybe you can have a look and see if there's any problems glaring you in the face that I've missed?
I'm thinking my "constant drip" is actually more of a "constant flow" system, the problem is I don't know the correct terminology for a lot of what I want to use, so my system utilises a lot of "thingys and doodahs" until I eventually track down the name of it from the very confused people at the DIY shop ?