I must admit I had the same dilemma recently as had some nice stuff to sell and it made up a full bike. I thought about selling separately but built the bike up a bit to see how it looked, after that I decided to sell it as a chassis and drive train but ended up adding wheels, tyres and the rest as a whole bike.
The parts were probably worth the value of the whole bike (excluding frame and forks) if sold on their own, but I did clear a big space in the garage, only had to send 1 box (albeit a big one) and hopefully there is one happy customer who received it (today according to tracking).
Sure I could have made a few more pounds, but in this case selling the bike meant more to me than the £.