[turboboy]

Thought I should update this to say that my cunning plan did not work, or at least did work initially but does no longer.

Bonnet was releasing fine for about a week and then went back to it's old tricks. Added another layer of sponge which worked for another week and is now back to default position of having to pull release lever once, pull up bonnet to disengage driver side catch and then repeat for passenger side.

It may be that the sponge sheet I used is not suitable and remains compressed after a period. Will have to look at alternatives once there is reasonable weather and I have sorted out the TRACS/ABS warning light problem that has now appeared!