Last thing I want is for GCHQ to know that I'm worried about them spying on me. Then I will properly be spied on.
I have no doubt you and I both are already 'properly' spied on. The Five Eyes agencies won't be taken to task for their transgressions by us hiding from them. At least this way we can contribute to an effort towards forcing them back under rule of law, finding out what they have collected and demand to have these records deleted.
I'm signing this with every address I have.
Maybe they should include a volume promise? For example: "We'll only take action if at least 100,000 sign up, and only then file all contact details all together. If we don't achieve this number by x/y/2015, we will not use your details without further permission from you, and will delete your details within 90 days of that date unless you tell us we can do otherwise."
But just think about it now, you're a dissatisfied citizen, and a silent one.