The word "information" is not really a sufficient clue that your IFR clearance has been terminated, because in France you can be flying on a Eurocontrol flight plan, at say FL080, Class E, and get a seamless radar service. Then if you want, due weather, a climb to FL150, you get a transfer to Paris Control, and the seamless service continues.
At no point did I make any reference about it meaning your IFR clearance has been terminated, indeed you can still be IFR outside CAS without a clearance. Certainly the hint about the point at which the clearance terminates would be in the initial clearance given on start up. If the flight (as far as we are aware) is going to be wholly within CAS then the clearance limit will be the destination airfield. If we know the flight will be going out of CAS when leaving the CICTZ then the boundary will be the clearance limit.
I hate to be the one to point it out but Class E is still controlled airspace, hence the seamless service as IFR flights require a clearance before entry and have to comply with ATC instructions. On the other hand, aside from the airways, the UK airspace that borders the CICTR is Class G which is uncontrolled, this is mainly due to the military not wanting to give away airspace it can use freely.