Been awake the majority of the night due to my mind not switching off, the night before i had been partying, could it be due to a hangover?

Post party insomnia: Alcohol though CNS depressant interferes with sleep cycle and causes alcohol insomnia. Dehydration may impact. Drink fluids , develop a sleep protocol like milk 1 hour before sleep ( trytophan makes you sleepy) a dark room, no electronic devices, soothing music ( like wave sounds ), that should help you relax so you can reestablish a sleep pattern. Melantonin/Valarian maybe of help. Talk to doc