On 14 June, I e-mailed Which? by responding to a message sent to me via spamgourmet. I had no response.
On 23 August, I e-mailed Play3000 by responding to a message sent to me via spamgourmet, ditto.
Which? have since responded to a direct e-mail that they have no record of the message via Spamgourmet. I did not receive an automated reply to it, and I did to my second message.
Similarly, when I e-mailed Play3000 directly today, I received an automated reply.
So I suspect the forwarding via spamgourmet is not working, at least for me or for these domains.
cheers
Lera