Neil, I can tell you that some years ago I bought a wrist blood pressure monitor for £29.99, they are available now for around £12 to £20. I put the serial number into Google and was directed to a Chinese website that was offering them for, get this, THIRTY PENCE each, but you had to buy a minimum of fifty and the shipping was free, then you have to add on import duty and VAT, so you do the math. Mike