I don't think that metal strip is actually meant to make contact with the cylinder wall - I think it's the bi-metallic strip which needs to move to operate? Anyhoo, I think there should be a light 'click' as you rotate the dial. In any event, if your programmer is set to DHW, turning the 'stat down and up slowly should operate the boiler. The 3-port valve might not actually move if only the DHW is on - I think it defaults to that position? So to test this properly, turn on the CH as well - that should get the 3-port valve in to the centre position, and turning the cylinder 'stat DOWN should then see it move to the CH direction. Anyhoo, you can buy new 'stats for a £enner on t'Bay.