Go for the condensing boiler. The lack of expertise in your area can be mastered by the "foreigner" from the next village. Contact the manufacturer , adresses are available from the Sedbuk page, and they send you plenty of staff .Local duds shouldn't be supported , especially when their expertise work can kill you . NEVER run an exhaust pipe of an oil boiler straight through the wall ! This practice-as commonly seen here in Ireland- is illegal in most parts of the world, not only in Europe.
Any plumber that is literate ( even a none-plumber ) can fit you any boiler. As long as you stick to the manual it shold be o.k. .
" Plumbers " are not trained heating engeneers , if you feel the need to call yourself a plumber there is no one who can forbid you that . " Plumbum " is the Latin word for lead . As heavy as the element is as slow is the congregation . Lead is very bad for the brain, as longer someone is exposed to it as worse it gets . Learning difficulties are part of the problem .
Fire your plumber ( that's a good one ! ) and get the good people in . " Heatmerchants " or any other boiler trader will recommend you plenty of trained and certified staff .