If the modules in the UK much those of a Greek university then you should not have to take exams in other modules in Greece, maybe a few if you get unlucky. DOATAP uses a percentage scale to calculate this but they don't reveal what it is(talking about transparency). I know it is more work for you but it would be a good idea to compare the modules before applying. You said that you don't mind sitting further examinations in Greece. Careful what you wish for because the number of extra modules can range from 1(usually 2) to 7,8 for universities such as Polytexneio, Aristoteleio, Patras. This means, attending a Greek University for lectures, laboratories, exams etc etc, also there is a long waiting list, some friends of mine were waiting for two years before being able to enrol for the extra modules in a Greek university (Aristoteleio).If you have money and time to waste, then this should be no problem but most people don't have this luxury. As I said before, the Bologna Convention will be enforced upon all member states of EU soon, so you might get lucky and avoid all these obstacles.