Each 2d barcode is unique to each individual stamp, so in theory it is possible to use it for tracking the letter/package it is used on.
However, Royal Mail do not offer any form of tracking or delivery confirmation on any basic 1st or 2nd class ordinary letter service, and in any case there is no tracking done within Royal Mail system from the 2d barcode on the stamp. So, no you can't use the barcoded stamp to track the letter or package it is used on.
Delivery confirmation for 1st and 2nd class Large Letters and parcels is carried out, but only where they carry a Post Office Horizon label or a Royal Mail 'Click & Drop' label, both of which carry a QR code.
If you want tracking throughout the journey of the package, you have to pay extra for it.
As an aside, you can scan the barcode on the stamp with most basic code scanners (many smart phones have this ability), but it won't tell you much beyond the source of the stamp (ie. counter sheet, business sheet, booklet etc) which you can usually find anyway from a code in the iridescent overprint on the face of the stamp, and the date of printing (again, there is a code within the overprint on the face of the stamp), its face value, along with its unique identification number.
