Thanks to TS on the forum, who came across a quote by Andrew Davies, here, regarding JJ as Mr Tilney in Northanger Abbey.

"I think JJ Feild is very, very nice casting for Henry too. It’s not the easiest part because, at the beginning, you could think he’s being a bit patronising and teasing towards Catherine. It’s a very difficult, delicate line to play and he plays it very well. Also he’s tall, handsome and very, very sexy. I mean, I’m probably not the one to judge, but the women who have seen it tell me he’s very satisfactory!"

We agree on the forum, that he sums it up very well indeed!