Im about to rebuild my wheels with new tyres and was wondering what people do when they run tubes. I have Michelins on ally rims but not tubeless so not sure if I should run rimlocks or not.

 If the rims are not tubeless, then always run rim locks.

If your drilling the rim to fit the locks, check where the join is as you obviously don't want to drill there. Good wheel builders generally put the joint opposite the valve hole. Most people run 2 locks on the rear, but 1 is fine. Choose the position carefully to give as much space as possible for the nut/spanner.

You must have one in a tubed tyre at low pressures, when riding green lanes with the TRF I've seen loads of guys lower their pressures and then without rim locks, wheel spin everywhere eventually ripping the valve out, even when they'd previously seated the bead on the rim. It's not worth it ruining your day, put one in!

Use two, and get the right size as they are different. Obviously some are made better than others, some just squash the tyre bead against the rim others clamp more positively. Use at least one on the front as well.

I would also suggest using two in the rear wheel and one in the front. It can be difficult to stop tyres moving on the rim on some bikes,my AJS rigid uses Dunlop chromed rimes and IRC rear tyres are very keen to move on them. I cut a section of a worn out tyre to use on the rim to see how well the rimlock could clamp the tyre. Some rimlocks are a waste of space,the ones I have now seem much better,but for the life of me I can't remember what make they are...