>to maintain the capability for the security services to access certain data on terrorists, criminals and so on.
In that case target the terrorists, criminals and so on not the innocent.
>It will not be looking into emails in real-time.
This is more worrying than it first appears. Forget the definiton of real-time, in it's ambiguity it implies that there will be the ability to read emails at a later time which would involve the storage of the content of emails and by extension other communications, something which they have so far skirted around and not out and out denied.