I wouldn't worry too much. If it has had its 12k service then most bits should have been taken care of. For example, at the 12k service they are supposed to replace the fork oil...point being that this is quite an extensive service and covers most things that you would look at in perhaps more detail if it hadn't just been serviced. Who did the service? I would place more faith in a 12k service carried out by someone like techmoto/JHP/Cornerspeed say than a main dealer such as OYB etc.
The main concern I would have would be the rockers. Have they been checked properly (ie the cams have been pulled). If they haven't and you find that they are shot...your looking at several hundred pounds to sort.
Anything else you decide to change/fit after that is pretty much upto you. I did certain things for piece of mind, such as a new chain and sprockets, brake pads to my preference, tyres of my choice etc. But basically you could buy it, and once given a service, ride it for another 12 months without spending a penny on it.
Don't be scared off...they are actually not as bad as the reputation that preceeds them....honest