Ok so fitting my additional side lights didn't go well. I added them by cutting the side light wire then butting the cables together with the new wires.

Took the side light out and made it all up. Tested it with power and worked fine, put it all together and tested again and I've now a light down. Either something came loose or the led died.

My question for now is is there a way to remove crimps without just cutting them off?

Not easy as they're designed as a 'single use' connector.

What you can try and do is remove the insulation carefully with a blade and then squeeze the flattened edges of the crimp with a pair of pliers. This will cause the crimp to open out a little in the centre and allow you to withdraw the wire's core.

Be wary though that the strands often get damaged during crimping and will not be as strong once exposed again and are prone to breaking at the point where they were previously crushed.

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Sounds a bit of faff! Given the wires had started to stiffen I think replacement may be better than repair. Having been crushed and weakened it may be a wasted effort seeing a new one is only around a tenner.