After getting my teeth into it this morning I searched you tube and found this video
BUT it was someone in the comments that posted saying to remove the push rod from the lid (1 screw) and poke it into the release catch and BAM! opened
Rather than edit or delete my post I thought I'd add this in case it helps some other 'locked down dad' get it sorted lol.
Excellent site and forums, bookmarked and you'll be the first place I come to for spare parts in future
Just to add that it's best to re-attach the rod to the lid (clip it over the front first) then align the lid and screw holders to the bin part, turn it upside down with the lid open (DO NOT close it) and then you can see the rod and can guide it into the hole whilst holding the catch to push it down. Put the whole part onto a surface with lid open and put the screws in then close the lid.