One of my oil cooler hoses developed a leak over the weekend. Topping up with water before I drove anywhere got old quickly so I replaced both hoses over the last couple of days. The main lesson here is to replace all your old hoses when one starts leaking - something I didn't do two years ago when I started this thread.
They're known to be a pain to get to, I removed the: air filter box and pipe, heater core hoses, EGR and housing that the intercooler pipe connects to, exhaust manifold heat shield, and the housing/manifold that attaches to the same housing as the water pump and has the bottom radiator hose attached to it.
I took the old hoses to Repco and bought two Gates hoses (02-0136 and 01-0005) that I was able to cut-to-fit, although a little bit of hose clamping finesse was required to make sure the one closest to the engine attached nicely.
The photo was taken just before I attached the housing/manifold to the water pump housing (just used some silicon gasket maker) and put it all back together.
Overall, not the hardest job. Could get it done in a few hours if you had the hoses to begin with.