Calathea W

I had one of these in our previous house and it died, but we struggled to get the temp over 14C in the winter, so I blamed that.
We're in a new house now, much warmer, and I saw one for sale, so thought I'd give it another go. Research suggested a not-to-bright, warm, humid environment.
I potted in regular compost in a plant pot and put this inside a ceramic pot with no drainage, with the internal pot raised 2-3" on some stones.
I stood this in a saucer and kept that filled with water so it could evaporate and keep a moist environment around the plant. I also misted 2-3 times a week.
It started to curl at the edges, so I put a reptile heat mat under the saucer and it's gone from bad to worse :( I'm still misting. I try to wait till the compost is dry before watering, but this never seems to happen, so it's over a week between waterings, when it gets about 500ml with baby bio in.
As these are sold in diy stores, you get the impression they're easy to care for, perhaps they're not?
Any tips very welcome, I'd love to save this plant, the last one was so lovely with its furry leaves and the way it opened and closed them

 

I think that it's a case of them being easily (= cheaply) propagated.

I would try it in the bathroom. Despite your best efforts you're not really raising the humidity.