very nice, love those oh-so-nineties pink! if you decide one day to do a sex change operation it will fit you great
The one thing i dont understand is what is going on behind the cylinder, on left side... looks like you have the e-start alternator cover but without the e-starter... can you take a close up pic? odd...
if you havent cleaned the carbs then do... but from my experience it is never a reason for a bike not starting "all of the the sudden", specially if it was running before and fuel gets to the carb.
just dont do like some people (also in this forum) who clean the carb ten times hoping that the problem will go away through cleaning and not fixing
You say you have spark, but just to make sure: disconnect the side stand switch, sometimes it plays mind games.....
If you see good spark when you take the plug out, then try to see that you still get good spark with the plug back in its hole and another one connected to the lead. When there is no plug, engine turns around easy and fast and you might see a spark, but with a plug mounted maybe not.
if it's kickstart model, check that the de-compressor system is not holding the exh. valves open slightly.
then after hearing about the oiling problem you have it could be simply a motor with very low compression thats blowing oil past the rings, sending oil to the breather/filter. An engine with weak compression sometimes starts ok when cold but becomes a bastard to start when hot.
try to do a compression test at a mechanics garage and tell us what result you get. I still suspect there was a reason you paid only 800 euro....

it's too nice to cost so little.... hope im wrong