Underground I use a 7DayShop travel pro tripod, about £50-60, very light and easy to set up but a pain in the arse to have full height cos of the way the legs extend. overground I use a Manfrotto 718B (£25 second hand) as it's a bit easier to set up properly for a full height photo; it weighs a bit more than the 7day thing but is a joy to fully extend.