Hi Chris
If you look at the holes underneath the pot can you see white roots? If so they need repotting.
Using a bigger pot (deeper and at least 2 inches larger in diameter), prepare by putting in some compost to a depth such that when you place the smaller pot inside the larger pot, the compost surfaces are the same?
To re-pot, loosen the sides by gently squeezing the sides of the pot (assuming you've got plastic ones). Hold the plant stem gently at the base, turn upside down and gently pull the pot away from the plant and existing compost. Provided the compost is not too wet the roots will hold the compost together. Insert this into the new pot and fill sides with more compost. Water ... done.
SnS

ps: try to bury the nobbly bits at the base when you transplant them. It sound like they're too exposed. These will root.