Thecontract with the guttering company would have been subject to implied terms that the work would be done with reasonable skill, and the items used would be fit for purpose and of satisfactory quality. It sounds as though that is not the case. Give them a deadlinein writing to come and put it right, and if they do not, then get a quote from another company to put it right. You can then bring a claim for damages in the court. It will be a good idea to take photos to show rthe problem, and if it is going to be an expensive or complicated job, it may be necessary to have a surveyor look at the defective gutters and provide a report.