That's 12 days without a working shower. Could be worse.
A few have suggested rigging a hose from the sink or bath to the shower. Some others have suggested removing the shower head and replacing with a smaller one to improve the spray. Also, the old head may be full of gunk too.
Although any plumbing I've ever done has ended up not quite sealed properly when put back together. I think I'd rather wait.
I hope to get lots of gross photos of gunk filled pipes when it all happens.
The hot water preasure in all the taps (except one, see below) is great now, better than the cold. The system is not as big and ugly as I expected and by pure luck it's almost the same colour as our house so it blends in nicely.
It's steaming away out the back now. The dog isn't too sure about this rumbling, hissing monster sitting just around the corner in her yard but she'll get used to it.
Unfortunately after all of this, the water preasure in the shower has dropped to almost nothing. It doesn't make any sense.
So no fear of sudden boiling water explosion from 40 year old electic system in roof. Yay!
But crappy hot water preasure that makes the shower almost unusuable. Boo!