Do I really need a separate business bank account as a freelancer?

Strictly speaking, no — as a sole trader there's no legal requirement to have a separate business bank account, and HMRC won't penalise you for using a personal one. But honestly, almost every freelancer I know who made the switch says it was one of the best decisions they made for their bookkeeping. Having all your income and expenses in one place makes your tax return far easier, reduces the risk of missing allowable expenses, and looks far more professional to clients. It also makes it much simpler to spot problems like late payers early. There are several UK business accounts aimed at freelancers with no monthly fee, so it's worth comparing a few — just make sure the one you pick lets you export statements easily for your records.