pmh1234 and trevs99uk,
Very usable information. Thanks a lot
I have read the "Guide to visual flight rules in the UK" which covers the UK airspace, ATZ, MATZ, standard overhead join, LARS, etc just as the "reference guide to uk phraseology" which contains the service terminology. In this way I hope I'm somewhat prepared.
pmh1234, I have found this chart which shows the LARS units with their appropriate frequenties.
http://www.nats-uk.ead-it.com/aip/cu...6_1_6_3_en.pdf
Regarding the VRP's, I was not aware of the fact you don't actually have to fly overhead those 'reference points' but I have just read the AIC 98/2005 concerning VRP. In my opinion this manner is much safer than the visual reporting points we use and have actually to be overflown.
The name Deepak is already added to my 'useful phone numbers, address and persons book' 
so I hope the problem with the flight plan is over and done with.
Today I received an answer from AFPEX as well as from Belgocontrol.
As expected AFPEX told me they can't give me acces because I'm not resident within the UK.
"
AFPEx is supplied, for UK based pilots flying to and from the UK FIR's, by Nats on behalf of the UK CAA and as such is not available for pilots outside the United Kingdom."
Belgocntrol answered me that at this moment it's not possible to submit a flightplan when the Belgium FIR isn't involved with the flight.