Why is UK being hit by medicine supply shortages?

Why is Australia being hit by them? I thought this was just an Australian thing... A few years ago Metformin - a diabetes drug with many generic brands was in low supply. Two years ago my birth control (the only norethisterone only pill in our market) was unavailable for 6 months out of the blue. Starting around September last year the medicated eye gel I need was unavailable, no other product in our market with those ingredients... it has only recently become available again last week. I bought 3 tubes.

To top all that off, late last year we find out that 50mg vyvanse - an adhd med my daughter and I are both on - is unavailable and won't be available til maybe the end of the January. Of course 50mg is the most common dose and our psychiatrist was away for the holidays, leading to a mad scramble for our GP to request emergency permission to prescribe and the psych to pause his holidays to write letters authorizing prescribing to dozens of GPs for his patients. We now have had to pay twice as much and drive to neighbouring towns and sometimes multiple pharmacies, to get 20mg and 30 mg.