Thanks all for your replies. Spoke to the supplier and unfortunately, the braces are glued and screwed. They actually suggested against putting in the extra braces that I was considering. Reckoned it would add that much more to its rigidity. I tried to remove the screws but they just won't budge...
Newbie here so apologies if in the wrong topic, but I've stupidly bought a left hand hanging side gate whereas I should've bought a right hand hanging one. Schoolboy error in that I didn't read the small print that said "if you want right hand hanging, let us know". What a plonker! It was made...