I have been buying my lancets and test strips on Amazon and have recently become aware that they should not have been charging VAT on my purchases. Two questions - how do I stop this for future orders and is it possible to get a refund on the VAT I've paid to date?
You should be able to inform the seller to stop charging you VAT, and fill in an online VAT exemption certificate.
I doubt you can reclaim the vAT already changed although you could ask HMRC.