The way you describe it seems like a very odd choice, as I'd expect a UK company to be more familiar with UK regulations and practice, and in your shoes I'd be wary of a company that had no history of UK expertise acting as the final design authority.

So, I presume there is a very good reason they are wanted in this role despite this limitation.

To make it work, , I'd expect them to take on someone with a UK background for the task. at least in a consultant role, and to make sure that the folk they deploy have been suitably boned up  and know not just '7671, but the relevant bits of other building regs, such as fire and structural, CDM and  working at height rules, the interaction of IDNOs, DNOs and BNOs, ESCQR and all the other things that can trip up designers used to working in places where such things differ and avoid them trying to plan things that either

1) cannot be built or

2) cannot be connected or

3) cannot be maintained

apart from that its all plain sailing...

Given you mention HV and LV, I assume there will be private transformers, and that is particularly germane, as many other parts of the world, even the 230V parts, are very different.

Mike

Hi Chris,

To answer this question I think about how we (a UK based design consultancy) would consider our competence when we are undertaking commissions for work in other conuntries.  The answer is that we assess where the limits of our comptency are limited and work only up to that point.  The gap between where our comptence takes us and the complete design is then bridged in-country, either by a local consultant or by local contractors depending on the location and procurment route.  in our case our competency differes depending on the particulars of the project and whether we have any previous experience of the location.  There are some locations where we would not undertake any meaningful design work because our knowlegde of the requirements in that country is so low that it would not provide any value.  

In your case its hard to be specific without details as to why you need to use a non-uk based design firm, where the non-UK based design firm are loctaed and whether they already have experience in the UK market.  If no previous experience and the are in part of the world that does not use Britihs Standards then i would expect their input to be limited to concept design, with detailed and technical design being undertaken by a separate resource that can demonstrate knowledge, skills and experience in specific UK requirements,