Window to French Doors

You would need to liaise with the contractor on colours and style he then should size up give a quote The contractor would normaly buy the materials used if you wanted to source it yourself again ud need to liaise with the contractor

It’s down to you to decide what door you want and ovbiously the opening size needs to be done by a professional and install lintels or catnips etc if need to change the size to suit door size, colour etc is down to the customer by the builder can order the door for you at your choice from where they get there windows or doors supplied

I personally mostly request that my customer orders doors, windows and fancy radiators, light fittings themselves, this is entirely because orders are usually made online and are sometimes damaged, it’s easier for the home owner to do a return. When I need to order doors & windows, then I would subcontract a proper FENSA Accredited window company to supply and fit, so then you get a guarantee with them.

Have a chat with your contractor and see what they advise. They may be happy with you selecting the doors and ordering them to their measurements or they may wish for you to let them order it.

You can do either , the probability of you as an individual customer getting it as cheap as the builder Is unlikely, but the builder who gets a discount because of how much he buys would charge roughly what you would get as a one off. So whether you buy your doors yourself or get the builder to there would be next to no difference