persoanlly, not sure what laws but here in Aust, caveat emptor applies ( buyer beware),

you were probably excited etc and checked the bike and went along and took what he said as being gospel. What i find odd, is that you did the checks after the bike you bought and found out the serial numbers etc. you should have done that before you purchased the bike. hard truth, lesson learnt. the guy may have also been honest etc and henuinely not known.

the surging etc can be fixed and happens to most , common fault. put it in your memory banks for next time, get on the bike and ride. i just purchased another one 2 weeks ago, and i do all checks, stolen, fininace owing, history etc....i would be more worried if you bought it and found the engine was knackered and done over 100K, .

move on, smile, and have fun