Ok,
kaneohegirlinaz, I finally got round to fixing the anthurium. Went to the garden centre and bought a big sack of peat moss, then picked out two plants which needed repotting. You can see in the first picture that the stems are long and there's a bunch of roots on the bottom:
First of all, clip the bottom roots off. Too many roots means the plant uses all its nutrients for the roots, not the flowers.
Second picture - plants with the roots trimmed, long stems:
Third picture, I cut off between 6-10 inches of the stem:
Fourth picture: I cut the stems into two or three pieces, and just stuck them into the peat:
I'll keep them well watered and, in about 3-4 weeks, I should get a few new leaves appearing. Then, instead of two plants, I'll have seven.
The two original plants were just stuck back into the pots, and they'll continue growing: