I got into the habit of flashing any large overtaking vehicle once it's cleared the front of my vehicle when we had the Dyane. - Artics, long wheel base lorries, caravans, anything longer/bigger than a standard Transit really - and I've just kept up the habit. I find most are grateful and appreciatively give a flash of the hazard lights in acknowledgement.
I don't tend to left indicate if just doing a normal overtake on a 2 lane highway - I do right indicate when starting the manoeuver. I pretty much always indicate appropriately on multilane highways - Motorways, dual carriageways etc - when changing lane either left or right just because I feel it clarifies my intentions amongst the generally fast moving vehicles.
Edit. My Ibiza has the "soft trigger" 3 flash indicators which gives 3 flashes of the indicator lights if you just partially pull the lever - not far enough to lock it on. I first came across this in the States and I really like it. I use it most for doing that left flash after overtaking.
I don't tend to left indicate if just doing a normal overtake on a 2 lane highway - I do right indicate when starting the manoeuver. I pretty much always indicate appropriately on multilane highways - Motorways, dual carriageways etc - when changing lane either left or right just because I feel it clarifies my intentions amongst the generally fast moving vehicles.
Edit. My Ibiza has the "soft trigger" 3 flash indicators which gives 3 flashes of the indicator lights if you just partially pull the lever - not far enough to lock it on. I first came across this in the States and I really like it. I use it most for doing that left flash after overtaking.