Hi Hafod, do you have a particular purpose in mind (may sound like a silly question but it would help to know ultimate use - for people of animals for example?). Some of the simple things like basil, lemon balm and even rosemary are pretty good, as is lavender and, of course, citronella. It depends if you want the plants to do the job themselves, or are planning on making something with them. I don't think I'd grow tansy again myself, unless it was for use with animals as I personally don't like the smell.