In the case of damaging a uPVC window, many people opt for replacing the window, however uPVC windows can be repaired provided the parts used are the same as the window damaged.

Depending on the type of repair that is required, you may find that the process will require a different person.  If the locking mechanism has become damaged, then this can be inconvenient to fix, as the components of the locking system are usually contained within the frame itself for security purposes. 

If the frame itself has become damaged or cracked, you should consider replacing it to ensure that it remains safe in use.

With older windows, you may find that the seal on the double-glazing panel has started to leak.  If this is the case, you will often see condensation forming between the panes of glass - we often say that the windows have blown.  While it is possible to correct this type of issue, in most cases you will need to replace the panel.  Your local installer will be able to advise about the most cost-effective way of fixing a blown panel - whether it is possible to simply replace the glass, or whether it would be more sensible to also replace the frame at the same time.