There are two versions of the digihome dtr80 which are made by Vestel. If you look underneath at the product sticker you will find one of three numbers:
T810 : In this case youve been conned into buying a digihome pvr80. This has very limited functions and cannot series link.
T816 : This does support series link but you need to install new firmware using a computer a a serial extension cable. You can get the firmware from here: http://www.futaura.co.uk/vestel.html
You want version 6.8. Bear in mind there areside affects to this program such as recording every episode that comes along on that channel and a very sluggish interface.
T825 : This does support series link by default. You go to the epg, highlight the program you want to record, Press the OK button and a menu will appear. Select series link.
Please be aware series link only stays active for 13 weeks so you will have to redo it halfway though a series.