I just ordered from here if you still need them: https://www.amazon.com/dp/B005DEK990?psc=1&smid=A3KGCU4HM6EAVD&ref_=chk_typ_imgToDp

It’s nearly impossible to get melatonin into the UK atm. I did order this same brand from Amazon in 2019 and it came in like 3 weeks so this should be fine

Edit: also 3mg is a high dose so you can snap them into quarters/thirds and it’s easily over a couple years worth of semi regular use