Ok I ended up having a win without having to pull the whole front off as Harv suggested I may have to do.
both Harv and Clay were correct with the assumption that there was a groove in the safety catch part of the bonnet release and it wouldn't slide back to allow the bonnet to open.
It was obvious once I got it open.

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Up close

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To get the bonnet open without removing the grill, agree with Clay that if it was an FB it would be easier to get your hand through the grill to push the safety in while lifting the bonnet release but with the EK grill being narrower I bent up a bit of tube and was able to push in while lifting the latch.

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Smoothed the groove out with my little belt sander and now opening again nicely.
