Do I need consent to send B2B cold email in the UK?

Generally no, when emailing a "corporate subscriber" — a named individual at a company, LLP, or other body with separate legal personality. PECR’s consent requirement for marketing email applies to "individual subscribers", not corporate ones.

That means firstname@company.com at a registered company is usually fine; firstname@gmail.com is not, and sole traders count as individual subscribers even on a business-looking address. You still need a lawful basis under GDPR (typically legitimate interest), an unsubscribe option, and clear identification of who you are.