Hi Gary, I was looking for information regarding the cabin air filter for my 2007 UK LC 100 series (but imported to Ireland) when I came across your thread above. Like you, I purchased filters, a cooler box cover along with the small cover for the filter slot using part numbers gleaned from youtube videos from the US showing how to retrofit a cabin air filter. Again, like you, I discovered that the main cooler box cover was not the correct cover for a right hand drive 100 series and the filters were way too long.
However, I found a workaround. On removing the original cooler box cover I could see an outline on it where the slot should be. So I decided to cut the slot out (How hard could it be - it's plastic). I used a Stanley knife with a new blade very slowly and carefully at first and more forcefully once I established a groove such that the knife would not slip off to one side. You don't need to be super accurate as the slot is plenty wide enough for the filter and the slot cover has a wide lip covering the slot. It takes a bit of time but it's a one off job to create a cabin air filter. As I suspected, the slot cover is the same one they use in the US and it fitted the cut out slot no problem. The UK cooler cover has the correct fittings on it to take the slot cover.
Finally I found that the Toyota filters have a piece of plastic in the centre which allows you to cut off one half of the filter and this happens to be the correct length for the UK 100 series. You also have to cut a few other pieces of plastic from the filter to get them to fit (it has 2 filters) but this is all very easy, being plastic.
Having looked into this issue a lot online I came across a guy in Australia who does sell the correct UK covers with the slot in place, but it is so easy to cut the slot in your own one - why bother?
I only found the problem of having the wrong cooler box cover (ie for a RHD LC 100 series) once I removed my own cooler box cover. I was encouraged to try this once I spotted the outline of the slot on the cover. I was also determined to try to achieve this after changing the cabin filter on my daughter's vw golf (See photo attached) and my wife's Toyota Auris cabin filter which I didn't photograph, but was a lot worse.
One thing to mention is that removing and refitting the cooler cover is not very easy. You can work it down towards the floor on the passenger side footwell. Remove any floor mat to make it easier but it involves a lot of manouvering the cover and pulling the dash plastic under the glovebox out carefully to get protruding parts if the cooler cover past it.
I hope this helps but get back to me if I can provide further clarification.
