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Composite hardware is fairly common, genuinely waterproof boots, less so. But unless you're stood in ankle-deep water for any length of time, you don't need it.
Toe caps wouldn't be a bad idea if you're kneeling a lot, but wouldn't swing it one way or the other for me.
Honestly, you'll be fine with whatever your local merch has in stock around the £45 mark (but Magnum if you want a specific recco).
Site electrician. Needs composite sole and toe rather than metal, above ankle cover. I want waterproof and not overly heavy (but non metallic toe and sole plate go a long way with that).