Looking again at those pictures I’ve decided that the lens of the light is not damaged, confirm with the seller that the tab is the only damage/repair and that it’s solid, if it is I’d buy it, that tab will be hidden anyway, as long as it’s strong and water tight and in the correct place (which it looks to be) you’re good to go, you could always have someone improve the tab repair if necessary, but like I said, it will be hidden, at 300 odd pounds and considering your excess, get it bought! Get the bumper sorted at chips away or such like and I’d expect you’d be all in for under £600, plus you could sell your cracked light for a few quid too.