I'm creating my won wiring loom on a Sylva J15 build and I have a small dilemma around relays.

I have power posts for direct from battery and switched from ignition.

I cant decide whether to use a relay for the ignition switched post.

Theres not much that feeds from that one but if I dont then I guess I should use a relay for the sidelights.

If I did use a relay for the ignition could I get away without a relay for the sidelights? The switch takes 11A continuous?

I would not use a relay on the ignition circuit - asking for trouble that is!
Unless you are using toy switches I would not use a relay on the sidelights either.
Fused - yes.

Most modern cars use ignition activated relays, i see no problem with it. i even use relays to activate all my ignition switched fused circuits (one 60A relay does most of them at one time.....)
side lights are needed to be permanently live so a relay is probably not a good idea UNLESS your switches are not rated for the continuous current or you wish to use switches that are earth activated, in which case a relay makes it easier to get them all working as they should.

I guess the thing that made me think about protecting the ignition circuit with a relay is that the wires from the fiesta (ST150 donor) ignition dont look man enough to take too much load.
Even though my light switch would be man enough for the sidelights, the ignition wires dont look man enough for that load.
Although saying that my guestimation of wires ability to carry current is based on old style PVC wire not the new thinwall stuff. Some of the stuff Ive bought thats 16A rated doesnt look like it should be!