Hi VJay, not long got back from there after a month away. i have posted a few times recently about the route, and this is the one i took as always.
Dover Dunkirk, head towards brussels, pick up Antwerp, AAchen, Koln, Frankfurt, Nurnberg, Munchen, Vienna, Gyor, Budapest, Gyula, Arad, Deva, Sibiu, Rimini Valchea, Pitesti, Bucharest, Giurgio, Russe bg, from there you can head towards varna/sofia, depending where you want to end up.
We left the uk on monday, france monday pm and went a slightly different route on the way down because of visiting relatives in Vidin, so caught the calafat ferry.
For Koln we went into the town to get a hotel, for vienna, just near the airport was a services with a hotel ( both around 100euros ) there are cheaper if you look, ( you can get an idea from the internet for the BB group of hotels which are around half the price and recommended ) in hungary the hotels are cheap, as are romania. I was very impressed with the roads in romania ( only the main route ones ) and saw how they have advanced since i last drove 5 yrs ago. The villages were tidy, no kids begging for sweets, the hotels were great, will take euros, although i did go into one town to withdraw some Lei ( rumo money ) as you would expect, you can use a credit/debit card in most of the modern fuel stations, but the exchange rate is crap, ( do it on the frontier )