Mr Happy...I usually find snogging quite pleasant sitting OR standng...hmmmm...sometimes even lying down.

I don't have a guitar strap so play sitting down. No question that I sound better singing when I stand, but find playing awkward, so just try to sit tall. Most of the guitarists I've seen in concert sit to play. Michael Smith stands. The great duo Small Potatoes (who both play guitar, and other instruments, and sing) stand, but then, they have too much energy to sit.

In small venues, where frequently there is no stage, I think the audience likes a performer who stands, simply because (s)he is easier to see.