I am not clear what you are proposing. Will it be something like a construction site installation?

There will have to be a service head and a meter. Yes, you could get a supplier to fit a SP meter and then fit a small CU. If you fit TP from the outset, you will need a TP board, but of course you would be perfectly free to install just the one socket circuit.

No problem just utilizing one of the three phases for the temp supply (provided of course the builders don't have any equipment that needs 3-phase).

For a builder's supply, you might want to consider not using the supplier's earth but going TT instead - just because you'll almost certainly not be able to bond things properly on a building site which can increase some of the dangers with PME.

   - Andy.

If the 3 phase meter is installed then you could do worse than fit one of these 4 pole isos beside it,

https://www.tlc-direct.co.uk/Products/WYREC4.html

and then take L1 and N on some meter tail to any old single phase box with an RCD incomer feeding a board full of sockets. The switch stays and makes it easier to hook up and test the final 3ph board later.

I have used  a wooden trestle in the past (yes this sort of thing, really that crude ) with plywood board on it with a DIN box RCD and a couple of breakers on one side, and about 8 double sockets on the other  If the decorators are in as well, it can be waterproofed with a bin bag or two, This is for when all the walls are being plastered, and there was no wish to leave a funny patch where the temp board was. I have even been known to screw it to the floorboards for the duration,,,

The RCD means it is not so serious if the earthing is a bit hit and miss.

Mike

Thanks guys that was exactly what I needed. It will just be in one of the houses , il set a temp board as u suggest with a single phase board and sockets, just come off L1 and N

and balancing on the phases.

Check with the DNO -  some (WPD?) I've heard prefer people to put the normal single phase loads all on the same phase (L1 say) and use the other two only for 3-phase loads (e.g. heat pumps and EV charge points). The idea being that they'll then balance things by rotating the phases for each house connection to the main - and can get a better overall balance that way than if say a whole estate is done with all the cookers on L1, showers on L2 and sockets on L3 or similar not entirely random pattern made up by electricians.

   - Andy.

Some MOPs will fit these free as part of the meter fitting.  E.on comes to mind but I guess there will be others.

In my case it was a devil of a job to get the MOP NOT to install the REC4 isolator. However, Mike's solution seems ideal.

 A TT earthing sytem would be needed for builders temp as per reg 704.411.3.1