You're right. It's just three weeks. I've been getting chain rub and the noise has been getting worse. No amount of adjustment seems to sort it. I've just examined the 50T chain wheel with a magnifying glass, it's looking pretty worn out already, some teeth seem to have about a third missing from them. I touched one with a file just to see how hard the metal is - result - soft as sh!t, just as if it's aluminium rather than steel.
When I was looking I went first to my local bike shop - Solent Cycles. They didn't have anything in my price range and size. I also set a budget because as I've been recovering from illness, I was unsure how well I might manage. I ended up buying on the net from a shop about 120 miles away and paid £40 for Parcel force to deliver it. Returning it is not so simple, nor is popping in for the free service.
I do want to keep cycling, but this Claris kit is not impressing me much. Also the steerer has shaken loose three times in as many weeks - I've not offroaded it or anything.
I think I'll p/ex this at first opportunity. It's a shame, as I do like it as a bike.