count( distinct x )

Apologies if this has been asked b4, but got this result when
attemplting to search the archives on the website

Not Found

The requested URL /mhonarc/pgsql-sql/search.cgi was not found on this
server.

Apache/1.3.12 Server at postgresql.rmplc.co.uk Port 80

The problem I have is with this statement:

select count( distinct area ) from areapostcode where postcode like
'BS1%'

the above statement fails with
ERROR: parser: parse error at or near "distinct"

I am not the greatest when it comes to SQL, but the pgsql docs implied
that the above would work.

What I am trying to do is get a count of the no of matches from the
statement below
select distinct area from areapostcode where postcode like 'BS1%'

Not the count of:
select area from areapostcode where postcode like 'BS1%'

Can anyone help?

TIA
Bap.