Wouldn’t you just take the meds when you start your day/night, whenever that is? So if your shift starts at 6pm, take at 5pm when you’re waking up and getting ready, and it should wear off by the time you finish and need to go to sleep. Basically, you’d want to have the methylphenidate in effect when you’re awake and working. Surely the NHS doesn’t have rules about what time of day you’re allowed to take these pills?
One thing I might add, from my experience, I’ve had issues with Concerta causing insomnia if I take it at weird times out of whack with my natural rhythm. Not sure if this would apply if you’re deliberately shifting your entire sleep/wake cycle. If insomnia is an issue, you could try out Ritalin only, taken a couple times over your shift. It wears off quickly and usually isn’t as bad about causing insomnia.