At the risk of sounding contrary, and to partially reiterate Simon's point, if you're going the tripod route, go for the most expensive compact tripod you can afford! I've used cheap tat, which lasts for about two trips underground - one spectacularly destroyed by being dropped down the P8 canyon, just before the second eyehole pitch. I managed to retrieve all the bits eventually!
The second bit of tat broke my DSLR, as it was too wobbly to work properly, and on some rough ground fell over whilst my back was turned, breaking the camera motherboard. Cursing that time.
After that I used a Manfrotto field tripod, which at nearly 6kg is no joke - but I hauled that up many deep shafts. Eventually though, dragging it through the confines of Peakshole Sough finally killed my spirit, so I bought a very nice lightweight Manfrotto compact. The price makes me look after it more carefully, and I wash it down scrupulously after every trip. The guy in the shop reminded me that every part on a Manfrotto tripod is replaceable from their after-sales. So if a leg catch breaks, it's fixable. Not so with others.
So far it's proved stable enough, and folds up small enough to fit in my bag with the camera and two lights.