I am about to start a new self build house project. I am considering the question of a temporary electrical supply. Can someone give the the definitive answer to the question of whether 240V is legal on a single dwelling construction site. ? I appeciate that the majority of contractors use 110V but my question is, is this a definite legal requirement from a HSE point of view.

I have heard that 240V is allowed provided that ceeform connectors are used.

If I have to go down the 110V route I will have to buy all new power tools.

Yep 230V kit is legal on a site but other precautions have to be taken. Whole sheebang has to be 30mA RCD protected and ideally a 240-240v isolating transformer should be used. Heck you can use 11kV on a site if it's in the correct circumstances, and correctly done (ie for crane supplies etc.) hand-held stuff has to be 30ma protected, but RCDs fail so 110v with 55v to earth is used as eliminates most of the risk without additional special measures.

A good starting point is to get a copy of HSG141 "Electrical safety On Construction Sites" Then get a properly designed system put in. You can either build it to suit or there are ready built systems you can get from suppliers like "The Rubber Box Company". Why not get your electrician to design something which will give you an isolating transformer with downstream RCD protection and a second 110V transformer fed on its' own breaker?.

you can always get site generators that generate at 110V

lol yea if you like  

If you provide a 110V transformer at the source of the 240v supply at least you have covered yourself
If the tradesmen havnt got 110v and they plug into the 240 thats there problem if something happens
Seems like health and safety is all about covering your arse these days
As long as you provide a safe option, if they choose to take a different option thats there problem not yours

Basically just cover your own arse and provide a safe way for the contracters to work,then if they want to take the risks thats up to them