I too have diverted to make use of facilities only to find there were none and a quick scamper off to the nearest bushes was the best option.
Flying with a full bladder is one of the most stressful experiences of my life and I will always divert rather than suffer.
At 6ft,4 the thought of using a recepticle in a light aircraft does not appeal to me and I dont think my passengers would appreciate it......
Anyway, the diversion was into Plockton whilst routing to Broadford (Isle of Skye). For those in the know there is only a few minutes between the two but the situation was becoming desperate.
Another was into Oban whilst routing from Inverness to Islay, this time it was a squeemish passenger that spent too much time staring into their camera and not enough time looking out at the scenery.