I've ordered some 2ba screws (cap heads for easier fitting)
hope that's the size. looks like po has forced 2 strange Philips heads in there as they are very tight and not an easy run in thread.
if I have to retap box I'll be mad..if so think it would be easier tapping out to 5mm?
That plate has 3 screws, one of them is above the cable in your pic. Try running your finger round it and you should feel the other screw or the hole if the screw is missing