[Exim] Multiple local_domains lists

Hi,
I'm just converting from exim 3 to exim 4 (and making things a bit neater
than they were), and I have the following situation :-

local_domains is defined as a file lookup
local_spamcheck is defined as a file lookup

Basically, domains in the spamcheck file go through a spam filter, and the
ones in local_domains files don't, but are still accepted as local domains.

The spam check works no problem, BUT, I can't figure out how to make the ACL
work properly - it works flawlessly if the domain I want to spam check is in
local_domains as well (presumably because the verification is done by
local_domains, then routed correctly via local_spamcheck). I've tried every
combination I can think of in the ACL :-

  accept  domains       = +local_domains
          endpass
          message       = unknown user
          verify        = recipient

  accept  domains       = +local_spamcheck
          endpass
          message       = unknown user
          verify        = recipient

Doesn't work (reports highest MX priority is local host, rather than accepting
the domain as local)

Numurous other combinations of accept domains =
+local_domains:+local_spamcheck, two domains lines etc have also been tried.

Any pointers?

Thanks,

Dave.