I must admit this topic is a grey area for me. If I depart in the UK, with an IMCr, from an uncontrolled airfield in class G, into a cloud base of 1000 agl, climbing to an altitude of say 2000ft, which may only be 800 ft above the nearest obstacle, and not flying the semi-circular or quadrantal rule, is that illegal? At this point I will likely be talking to a radar controller OCAS but I have just said I am on a VFR flight because I haven't actually met the IFR rules at this point, and actually the clouds are only scattered and I think the rest of the flight at 2000 ft and I don't plan to actually fly according to the IFR rules.
This might be a typical departure. In reality I plan most flights using routes OCAS and altitudes that will make me compliant with IFR rules anyhow, but sometimes you cant always meet the rules, especially the quadrantal rule when there is lots of CAS above the class G. I have also heard some people say "xxxxx on an IMC flight from x to x....." but AFAIK this isn't a truly valid class of flight - its just VFR or IFR.
climbing to an altitude of say 2000ft, which may only be 800 ft above the nearest obstacle, and not flying the semi-circular or quadrantal rule, is that illegal?
Yes, it is illegal, if you in IMC you must fly IFR, so you must follow minimum rule. This is not valid for departures and arrivals. The famous 2000ft altitude made me chuckle.
Does the quad or semi rule apply when taking off or landing, or anyway below 3000ft?
During enroute flight in IMC one should be 1000ft above the obstacles, or 2000ft above if there is terrain above 5000ft.
The quadrantal rule applies on IFR flights OCAS above transition level or 3000ft, whatever is higher. I guess takeoff or landing will always be below transition altitude in UK.
Some countries like Italy and Portugal have a deviation to the semicircular rule. Their split is not East/West but North/South, fair considering the main routes are North/South. Will that change with SERA? Do you have to change levels like a yo-yo?
Most (all?) of the UK is now 6000ft TA.
So the semi or quad levels appear to be irrelevant for most IMC flight.
I have also heard some people say "xxxxx on an IMC flight from x to x....." but AFAIK this isn't a truly valid class of flight - its just VFR or IFR.
Yes; confusion everywhere 
Sometimes I might tell ATC I am in IMC if they are passing me traffic reports, but that doesn't seem to stop them passing me the reports.
FWIW, I have always flown at "funny" levels like 4300ft and have never had that queried in the UK. Only once in N France did ATC query it, in a manner which was deliberately ambiguous so they would not tell me what the rules were. They just wanted me to climb or descend to some semicircular level. I was VFR.
Back to my original question, it would be useful to know attitudes to "VFR" in IMC around Europe...
I know a VFR airfield where you see a plane depart into low cloud base, below MSA at specific times >every week, flown by ATPs.
What suprises me is that Germans do this at all, especially the high profile bizjet flights, given that >(reportedly) the only countries where pilots have been done for departing into IMC conditions were >the USA and Germany.
Interesting discussion. Departing IFR from an uncontrolled VFR airport is OK, at least in Sweden as I have learned from this thread.
For an airport with no aids (grass field without lighting) the lowest visibility needed is 500m. If you add a centerline marking or runway lights it's 250m.
You can of course question the safety of doing this.
