What is the ruling on taking a sum of money granted by some banks in Britain when transferring an account to them, which aims to attract customers?

It is impermissible to take this money because it is a gift in exchange for the loan. The rule states that every loan that draws a benefit is usury (riba). Scholars have unanimously agreed that if a lender stipulates an increase or a gift from the borrower and lends on that condition, then taking that increase is usury. It has been prohibited to give a loan that draws a benefit. If this is done without a prior condition, before repayment, it is not permissible to accept it unless one reciprocates or deducts it from the debt, unless it is something customary between them before the loan.