In what order should plastering & electrics be done?

First fix Electrics first (new wiring/boxe's etc), then plaster, 2nd fix electrics (Fitting's, lamps etc) Doubt the plasterer will remove/refix the skirting and dado, probably plaster to them.

first chase out walls for sockets and light switch,fix back plates to wall then run wires to where they need to go sheeth any bare wires then replaster room then 2nd fix

Hampshire carpenter is correct but they will remove the dado and skirting if you mention it at quote stage.Its unlikely they would refit it though.It sounds like you have a lot of work (with other job postings).A good builder will advise,plan and supply ALL tradesmen for your work and it would be much easier for yourself to leave them too it if your not sure on what order to do these jobs.It would also benefit you to have one point of contact rather than using 3,4 or 5 unconnected tradesmen.

Do all the 1st fix electrics first, then plastering, finish 2nd fix. What has the plasterer said regarding dado rails and skirtings. You could leave skirtings on, but it will be easier for the spread to remove dados, especialy if they dont have a deep profile, plaster could loose some of the depth.