You guys have already gone over the tank issue, my next thought is how on earth are you going to fit a Xanthosoma in there? Those are rather large plants, with even the "small" ones needing a vivarium of 3'-4' to fit in. You could try some of the smaller aroids, there are some tiny species of Philodendron, including one just labeled ecuador. I'm not sure what you have available in the UK, you could try some planted fish tank groups though if they're around, there are lots of smallish aquatic plants you can switch over to growing emersed. Are you going for a Peruvian biotope, or just want it to look good?