[strath76]

Sounds like you have already put a lot of throught into it. I would suggest something like a ventricosa or alata. alata comes in both highland and lowland so you should check this when buying. I f you don't mind hybrids then ventrata is a combination of the two.

I would give rajah and hamata a miss intially. Whilst they are great plants they can be tricky to grow and as this is your first attempt they aren't the sort of plant to experiment with. They can also be expensive in comparison to the other plants listed. Hope this helps your decission.