I guess deep down I'm just not ready to commit to someone in the same way so that's making it easier. But i'm also not yearning too. I'm busy with work, studying and renovating my house. Fitting in mountain biking (both for enjoyment and to build up a circle of friends which is going well) and the gym in between leaves very little time, certainly not enough to commit to a relationship.
So the current arrangement is ideal

If I start developing feelings towards her I'll re-evaluate, but I don't think I will. On one hand she is attractive, has a very good job with huge career prospects, has her head on straight and doesn't want kids at least in the near future. But on the other there are also a few reasons I wouldn't want to be in a relationship with her. I also don't think she's playing the long game trying to "win me over" as some of my (female) work colleagues seem to think. We discussed it again in jokey conversation at the weekend and appear to be on the same page - we agreed we are not exclusive but neither of us actually have time to see other people at the moment.
I passed my ex in the street last week, twice actually. Both times I smiled and said hi. Don't think she expected me to, so it was a bit of a delayed reciprocation from her. Made me feel like the better person