It is true that if you pitch up "IFR" somewhere, you do sound more like you know what you are doing. Especially if you give the next section of your route as several IFR waypoints, rather than a list of villages which the ATCO has probably never heard of.
On that basis you should be more likely to get a radar service.
So on this particular trip would it be better / advisable / possible to file an IFR flight plan?
No point. This subject is pretty complicated but basically if you file an IFR FP at a level below the airway MEAs, that FP will not go anywhere except departure and destination. It may be helpful to look for wreckage but that's about it. You may as well file it "VFR" and then you are not risking rejection by the Eurocontrol computer (all IFR FPs go to Eurocontrol for validation).