Im laughing... but only at the memories of getting my first road bike just like it, also coming from a mtn biking background. Like those above, as long as it fits, who cares. My raleigh sprint was a second hand and it fitted perfectly (after adding a 10mm longer stem and slightly longer seatpost). I got right into it and now to be honest, im a roadie. The only advice i would give is A) start off on quieter roads to build some road confidence up and B) if you get bitten by the road bug and want to do the bike up, plan wisely or prepare to spend lots. mine turned into a money pit. I did used to get a lot of satisfaction out of turning up to time trials etc on a jalopy and matching people on carbon for pace though!
one of my mates just got into road bikes and went down the restore and oldie route. he ended up just replacing the chain, brake pads and tyres for £40 and he was away.