Alien18:
how would on test the accuracy of such an item? Surely, if you're going to buy on of these, you don't already have one and therefore have no comparison. If you do have one already how would you know which one was accurate or nearest?
Well, you'd have to compare it to some professional equipment to know for sure. Personally, I know my expensive one is more accurate since if use a cheap gauge I over-inflate my tyres hugely and my bike slides all over the place. Honestly, £10 is more than worth it for the accuracy of a better gauge; don't skimp, especially if you ride a motorbike.