Not a big fan of Rohan myself though-I think they are over-featured, and didn't seem to wash very well.
Thaw (can order online) do longer length trousers in 33, which can be ordered over the phone (see www.thawonline.co.uk). I haven't quite plucked up the courage to buy some yet, as they are quite pricey, but when I posted a similar post, a lot of people raved about them.
Could try men's trousers (most women's ones seem to be copied off the men's one's anyway-but don't get me into a rant on women's gear...). Depends how small you are though and they still might be a bit short.
Alternatively, you might be able to find some casual trousers in M&S that are made of a suitable material (i.e. non-cotton)-they do a great range of sizes, and will be cheaper than getting something very specialist. Depends on what you use them for.
Post a review if you try something. Women's trousers are very underrepresented, and I'm still mulling where to splurge.