While I sympathise too, as your loss is so small (�10), I really think it is best put down to experience. In strict legal terms, you probably do have a case for negligence against the decorators under the Supply of Goods and Services Act - as they failed to carry out their work with reasonable skill and care. At the very least, they should have advised you that they had drained the radiator. But, in practical terms, it would not be worth your time and hassle to pursue a claim in the Small Claims Court and the district judge will not look upon a claimant favourably for wasting court time for such a small sum. I know it is the principle that matters, but, sadly, real life doesn't always work like that. There is certainly nothing to stop you trying to negotiate some form of 'compensation' with the decorators informally, perhaps with the threat that you will take some form of action. Tell them how much inconvenience it caused you (if true) - time off work etc. All too often though these little 'niggles' can take over your life, so perhaps it's best put down to experience.