I stuck my head under the car yesterday to have a look at the driveline (see my other thread about that) and I noticed some patches of what appears to be surface rust forming on some components such as the universal joints and shaft and some spots on the body.

Just surface stuff, but is this an issue and should I kill it with some chemicals?

I think that there is minor stone chipping happening which breaks the paint barrier and allows the rust to form.

I would say just hit it with some Killrust or the similar, but not sure how heat resistant it is.

just hit it with some rust coverter and than paint touch over the area with some body deader or even just some paint to cover the area