Ok, so I contacted a pharmacy and was told they would be able to order Nature-Throid even if my prescription is for Armour or Erfa, but only 30, 60, and 90 mg pills. A two months' supply will cost me 564€ (ca 400 £). That means that, if I do great on Nature-Throid and want to stay on it, I will have to pay ca 2400 £ a year...can that really be correct?! I thought Armour and Erfa were expensive, but they "only" cost me about 2000€/1600 £ a year...
When calculating the price, I assumed I'd need as much Nature-Throid as Erfa or Armour (7.5 grains of Armour and 8 grains of Erfa).