It's Not all packages that can be tracked and only those being delivered by Royal Mail can be tracked on the Royal Mail Site. Others, that are trackable, appear on individual Carriers sites.
I recall buying a very cheap fountain pen through Amazon and carelessly didn't note that it was being delivered from China. It took over three weeks to be delivered and proved to be a useless item. As it cost about £2 it wasn't worth the trouble of complaining; although I could have to Amzazon.
Hans.