[exim] spamassassin user filter setup

I have spamassassin successfully adding headers with the spam score and bar.

using:

warn message = X-spamassassin-score: SA score $spam_score ($spam_bar)

this along with the rest of the ACL lines successfully adds the expected header line.

I have created a user filter which looks for the bars, and SHOULD save the spam
email in a file - but it NEVER gets saved. The mail always gets delivered to the user's
mailbox. If I examine the mailbox - there's the mail WITH the spamassassin header line.

I have used:
if $h_x-spamassassin-score: contains "++++++"
    then save $home/user.spam
         finish
endif

The filter never seems to process this.
# exim filter IS set up, and indeed I use the filter file for many users, so there is not
problem there in general.

Is it possible that the added header isn't present at the time the user filter is processed?
I cannot figure why this entry is being ignored.

Thanks IA
Jim