There is no legislation which requires a higher rate of pay for overtime. My company pays 'standard rate' for all hours worked (including bank holidays) and many other firms do the same. This is perfectly legal.
It's also worth noting that the reason that hospitals have, for many years, forced junior doctors to work for 80 (or more) hours per week is that doctors' overtime has always been paid at LESS than the normal rate of pay. (The typical rate of overtime pay for junior doctors has generally been only ONE THIRD of normal pay. It's therefore been far cheaper to employ doctors on overtime than to employ more staff). So, compared with the medical profession, getting 'normal pay' doesn't seem so bad!
Chris