Sorry, but this has turned into a long one (ooerr vicar).

My place has a coach house, aka a 2 storey garage, which is paired with
a similar structure next door. The two roofs have a valley between them
and this was relined not long ago by my neighbour in zinc.

Every last leaf or bit of loose moss in the city seem to find its way
into this. Consequently, it blocks, fills and overflows into both
sides. I was reminded of this at the weekend whn I found a drip, so got
up there and cleared a clot of moss. Soon, it will fill with leaves
and, if we don't keep an eye, the same will happen.

The key to this problem (in my view) is the outlet, which is a running
outlet before the end, the end of the valley being blocked by a full
height (~6 inch) vertical 'stop end' formed to finish the zinc.

Of course, there's no sunstitute for regular maintenance but I would
rather devise a means where the need for this isn't indicated by a leak
inside the strucure, ideally without making a huge meal of it (ie strip
all the roof tiles and form a deeper valley). Had a chat with my
neighbour today and he's happy with whatever solution I come to.

Now, I reckon that reducing the height of the stop end would do the job
and it's tempting to just cut a deep groove in it. That way, a blockage
in the outlet would lead to water spilling out of the end, which could
be spotted and the blockage cleared.

Easy-peasy....but: I would like to ensure that when this overflows, the
water falls clear of the brickwork, so really need a bit of an extended
(3 - 4") lip on the groove and I'm trying to think of a way to form this
neatly. So far, I've thought of:

1 Getting another piece of zinc and forming an extended spout then
fixing this to the cut end stop. Probably the Rolls Royce solution, but
I'm not sure I fancy my chances forming a decent solder joint at height
in winter (I know about soldering zinc and it's a bugger).

2 Cutting a circular groove and laying a piece of grey mini drain pipe
in this horizontally, with about 6" protruding.

3 As 2 but with a piece of mini-profile plastic guttering. (I can't
seem to find a local source of zinc drainage or I would use that instead
of plastic)

The issue with 2 and 3 is securing the plastic pipework so it doesn't
slip out or in. A pipe or gutter clip might stop it slipping out, but
would look a bit of a bodge on the outside. Basically, I want to form
something, bet up there, cut the groove, and clip my piece in.

So....Any bright ideas chaps? (Or is everyone glued to the footie?)