Renovation and extension - when to order fixtures and fittings

[Bahhumbug83]

Currently 3 weeks into a 16 week extension and reno (and the rest!!) and just wondering at what point I should be ordering the following types of things:

-bathroom fixtures and fittings/sanitary ware
-kitchen appliances
-plug sockets, light switches
-lighting

We are having our kitchen profesionally fitted so I don't need to worry about anything other than appliances for there.

The plumbing work is being subcontracted out and I haven't yet spoken to the plumber.
Is it better to order sanitary ware on their trade accounts or should I buy these myself and store them until required?

I just don't want to be caught out by lead times and being forced to make decisions at short notice. The last thing I want is them making their own decisions!

Anyone?

Presumably you have a schedule of works? Ask the fitter , electrician and plumber when they need the stuff. I've always bought my own - whenever someone has said they can buy stuff on their trade account it's never exactly what I want, however things like sockets and switches, unless you have a particular look in mind I just let the electrician get them as those things are cheap. Lighting - if spots get the electrician to source them (he/she will have a trade catalog for you to look at), anything other lights buy when you see it - high street stuff can be delivered or picked up in days. Something off Etsy may take longer.
Once you have a date then check out the lead times. I find sanitary ware is usually delivered in 3-5 days, appliances the same unless something particular (like a aga or particular model washing machine). Tiles and flooring can take forever if they are on a slow boat from China! I got fairly innocuous tiles from Topps Tiles but had to wait six weeks, and ordered special cement tiles from Spain which took 12! So things like that you must check lead times and plan accordingly.
Sanitary ware and appliances can take up a lot of room, so aim to order them for delivery close to when needed, but not too close - last thing you want is trades standing around waiting.