What happens to my flightplan?

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Background: I'm a JAA (CAA) PPL, which I obtained in Florida. Never done a flightplan there (Flight Following was the way to go). I'm now flying (for over a year) out of EHRD (FPL mandatory) to controlled and uncontrolled fields. Depending on circumstances I submit the plan via the internet, from the EHRD briefing room or over the phone to the Amsterdam FIO. It all works fine but I still do not get the finer points of what happens with this plan. Could somebody (preferably from the EHAA FIR) enlighten me on the following:
- Okay, flightplan submitted and accepted. Where is it sent? Who all receive the flightplan? EHRD TWR for sure, but how about AMS INFO or Dutch MIL? My destination? Alternates? Or do they all have access to the same big database?
- If I depart from EHRD, I assume EHRD TWR opens the flightplan. What does this "opening" actually mean in practice? Do they toggle a bit in a database, or does it involve a call or message to somewhere?
- If I depart from an uncontrolled field, let's say EHTX, who opens my flight plan then?
- If I, on a whim, decide to ask for a sightseeing clearance into or through the EHAM CTR while flying from EHTX to EHRD, does EHAM TWR have access to a copy of my plan? If I knew I was going to ask for that clearance before I departed, would it have made sense to put that in my plan? If so, how? How about if I fly from an uncontrolled to another uncontrolled field (EHTX to EHMZ, for instance, no FPL mandatory), but want to fly through controlled airspace?
- Who closes my flightplan upon arrival on a controlled and on an uncontrolled field? Should I ask for this or is this done implicitly?
- How does communicating, opening and closing of a plan work on international VFR flights?
- The only route I have specified so far is the VFR departure from EHRD. Does it make sense for a VFR flight to put in a more elaborate route? If so, how do I do this if I "Follow Roads" instead of airways/VORs?
- I know that if I'm crossing a FIR boundary I need to put in an EET/ for the boundary. But the internet tool refuses multiple EET/ entries for a flight to, e.g., France. Is this a limitation of the tool or not?
- What happens when I'm overdue? Who is supposed to notice this, or is this flagged automatically somewhere? At what point in time can I expect a full-scale rescue operation to be mounted?
- I understand from various websites that the UK ATC system is a little "lax" (for lack of a better word; this is not meant as criticism) in closing flightplans, to the annoyance of FR/BE/NL controllers who are stuck with open flightplans of planes that have left for the UK, and whose plans are not being closed. Is this true? How do I make sure that my plan is indeed closed if I fly to the UK? Any other countries/places I should be aware of? Could someone from the UK comment on this whole "Responsible Person" thing?
- Anything else I need to know/do/should not do to make life of the professionals at the FIO and in the towers easier?
I have looked all over the internet and in my study books and there's not a lot of documentation on this stuff to be found. The best bit is the CAA document on FPLs but it only covers HOW to fill in an FPL form, not what happens afterwards.