Salaried staff usually don't get paid for overtime (although individual employers might make exceptions - I was salaried when I worked on the railways but still received some overtime pay occasionally).
Further, when overtime is worked there's never any obligation upon an employer to pay a single penny for it UNLESS
(a) the employee's contract states that they'll receive payment for it ; OR
(b) the employee's average earnings would fall below the National Living Wage (or National Minimum Wage, as appropriate) as a result.
Even when payments are made for overtime they don't have to exceed, or even match, the normal rate of pay. Junior doctors used to be paid at just ONE THIRD of their standard pay rate when they worked overtime (which is why they were required to work 36 hour shifts).