Do you have a pic of the carpet? Do you have the make and the company who supplied and fitted it? It might be possible to have a new piece of the same carpet just on the worn areas. As the batch numbers are different it may not be a perfect match but would definitely be cheaper than replacing the whole. It's also less wasteful. If you cannot get the exact carpet you may be able to make a feature out of the different replacement carpet on the treads if done right.
Isla Cherry
Sonia
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