The UK doesn't have blanket Class E, unlike the US. Except for around some controlled airports it's mostly either Class A, or Class G. Class A isn't a blanket overlying Class E - a fair bit of it consists of corridors along air routes down to the lower altitudes.
In class G you can be IFR to your heart's content. There is no regulatory requirement to talk to anyone. Not being controlled airspace, there isn't a controller, only a Flight Information Service available. Think along the lines of 'Inside CTA' or 'Outside CTA' and never the twain shall meet. Once you hit Class G airspace while enroute you are no longer 'in' CTA therefore no longer have an IFR clearance 'in' CTA. A new clearance must be obtained for the next bit of CTA you wish to fly in.
Doesn't mean you are no longer IFR though. You're IFR in Class G as long as you adhere to IFR. Conversely, you're VFR in Class G as long as you adhere to VFR. Curiously, you could yo-yo IFR-VFR-IFR-VFR as frequently as you like as long as at each change you adjust your mindset and follow the appropriate set of rules.
Last edited by Tinstaafl; 25th Jun 2012 at 06:00.