Ok so removed the front bumper from my badly bodged (by previous owner) 5 tonight and it was only held on by two small bolts/screws one inside each wing.
Upon removal I could see what appeared to be the left overs of two mounting brackets which poked out of the back of the bumper towards the engine bay. I assume there are more mounting points than just the wings as my bumper rocked up and down as it was pivoting on the wing.
Any pointers as the where else the bumper is bolted/screwed to the front end?