InvestEngine are offering a £25 sign up bonus for signing up via the referral link below as part of their refer a friend scheme. They don’t have a promo code, just a referral link to follow. You need to sign up, and top up your account with £100. Terms and conditions for the offer are available when you follow the referral link.
InvestEngine Referral Link: https://investengine.com/referral-welcome/?utm_medium=share&utm_source=growsurf&grsf=x907sk
InvestEngine is the cheapest Stock and Shares ISA available in the UK. If your goal (like mine) is to reduce fees and invest in Vanguard ETFs or similar, this is the cheapest option.