I've been working on a plan for a tile roof and built a small section for experimentation. This is in the USA (Florida) and the house has US "W" style tiles. I bought samples of 5 systems, 3 hooks and 2 replacement flashing.
Here are the hooks:
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The far one is Ironridge All Tile Hook, Middle one is Unirac, closest one is Ironridge Quick hook.
The clear winner is the Ironridge All Tile Hook.
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The tang is adjustable to 3 lateral positions and has a certain amount of vertical adjustment. In the above photo, it is adjusted to minimum height which just clear the trough of the down slope tile. In this position, the vertical clearance at the tile edge is 33 mm and it slopes up to 41 m by the vertical tang.
You grind out an exit path in the tile f the tang and then it looks like this when done:
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You don't want the tang to touch the tile so that when it heaves up or down in the wind, it doesn't crack the tile.
The Unirac is way too high and has no adjustment. The Quick hook is too big and costly.
The two replacement flashing types were not good in my view. They replace the tile with a metal flashing and it looks ugly. It does save the tile grinding, but that is really not that bad and the metal flashing has extra steps to put down.
I have no idea what the legal and logistical issues would be with using this hook in the UK. The tile there is built to different dimensions I am sure. One thing I notice is that the tile is rarely nailed or screwed down, it seems to be mostly hooked on battens, which makes it easy to lift up and work on.
Mike C.