Every episode in the series (all 692 of them!) were aired between 1997 and 2001 on Channel 5. Other UK transmissions have shown only parts of the series, which was actually made between 1979 and 1986. Presumably the money that broadcasters can get from selling advertising during the programme isn't great enough to cover the broadcast rights, so there's no commercial gain to be made from screening the remainder of the series.
This might bring back some memories for you:
http://www.wwwentworth.co.uk/
Chris