thanks for your reply "grocer" much appreciated, however here's my experience today for anyone who's interested.
i was told to go to the PANCRETAN BANK and ask for "PARAVOLA" (not sure if this is spelt correctly but thats how its pronounced in english) this is the form to apply for vehicle exchange,you get 2 at a total cost of 135euros. from what i can gather this is a set fee for cars regardless of engine size etc, because the assistant at the bank did not ask me for details of the car, only for my autograph twice and 135 euros.
then i had to take these forms and my passport, residents permit and tax number to the ministry of transport office where i met the seller of the vehicle and we proceeded to the relevent department.
we both filled in our personal details- address/contacts etc and then i asked the question about a reciept for tax declaration. the assistant produced 2 forms, one each for us to fill in our personal details again, also the fee for sale/purchase of the car.
i was given a temporary "cover note/registration document" for the car i had just purchased and the kteo ( mot ) document. i was asked to telephone that assistant on the following friday to see if the official registration document is ready for me to pick up, im not sure if this is the usual process because it was explained to me that the office i attended today was in the process of a big change in procedures due to other regional districts merging with the one i had attended.
all in all i was resonably happy with the whole experience which probably took about 1 hour from the time i entered the bank and left the ministry of transport building.
it is a more expensive event to transfer vehicle documents here in greece, so i would suggest to anyone else who is thinking of buying a second hand car in greece to take into account the fee etc when you are setting your budget to purchase a vehicle, also check the vehicle for tax and kteo (mot) as these can soon eat into your set budget.
beware these official goverment buildings are not very often signed up from the outside and when you get inside dont expect any signs to be duplicated in english. its a big help if you can get a local greek person/friend to go along with you, otherwise the whole process could take you much longer and they can also asked questions for you that your not sure how to explain.
happy days its taken 3 years but i finally have a greek registered car, i can relax now and mothball my old renault espace until im ready to drive it back to the uk, if i do,i might decide to sell it.