It doesn't normally take that long. does it appear on Parcelforces website? If so, what does it say, If it hasn't appeared on here it's likely lost in China, ask for a replacement.
If its showing as in the UK then ring Parcelforce and 'chase' it using the UL tracking number PF gives you.
This usually wakes them up, but last week my watch went via Nottingham as it went in the wrong van at the airport!!
If it says it is with Customs in Coventry DON'T chase it, it may, or may not reappear!
Rob