Redman41�s post might be misleading you. Your rights under the Sale of Goods Act are a completely separate matter from any guarantee that might be given.
Under your statutory rights, you�re entitled to the repair or replacement of a faulty item (for up to 6 years from the date of purchase) if it can be shown that the defect occurred due to an inherent fault (i.e. something which was wrong at the time of purchase). For the first 6 months after purchase there�s an automatic assumption (unless there�s clear evidence to the contrary) that any defect must be due to an inherent fault. Thereafter it�s up to the purchaser to show that the problem has arisen due to an inherent fault.
Where it can be shown that a defect has occurred due to an inherent fault (within the 6 year period), the retailer must remedy the problem, by repairing or replacing the item. So any rights you have under the Sale of Goods Act are with the shop or garden centre where you purchased the furniture, not with Kettler.
A guarantee is completely separate. It�s effectively a �gift� from the manufacturer (although, since you paid for the furniture and the accompanying guarantee it can be argued that you�ve bought a �service�, which the manufacturer is contractually obliged to provide). As such, the manufacturer is free to determine the terms of the guarantee. Kettler have either included a term stating that any guarantee runs only from the original purchase date or they�re relying on the fact that the �service� you purchased only gave them a contractual obligation to ensure that your furniture was kept in good condition for 5 years from that date. Either way, you haven�t got a leg to stand on.
Chris