Is there a problem with filing a flight plan? Some countries require it for all flights travelling further than 25nm from point of departure. If the system to file them is simple and efficient I wouldn't be too bothered - I did it for the better part of 5 years while flying in Canada.
The difference between having class E and class G around places like Exeter, Farnborough, Inverness, Manston, Norwich, Oxford, Southend, etc. would, to a pilot not "brought up" in UK airspace, mean receiving a service that is clear and familiar. Everyone who has a pilot's licence knows what separation is and isn't provided in class E whereas only people who have spent some time flying in UK class G airspace with an expert beside them will begin to fathom how it might just about work out to more or less the same thing. It took me a very long time to fully comprehend receiving a clearance whilst being uncontrolled, and requiring another clearance to continue once airborne. All a bit 1950s really.
With regional airports, outside controlled airspace, becoming busier and attracting more traffic, especially biz jets, realigning the UK's system with a well known international standard with little practical change can't be a bad thing? The class E airspace could even have operating hours to get around requiring 24/7 ATC coverage... Would still be clearer than the current mess.