You may have been in touch with builders, tradesmen and suppliers - but before you do any work at all on your build get the place insured. 

If you take out insurance at any time other than BEFORE you start work, you will be unnecessarily spending your precious budget as the insurance premiums increase if it has not been in place from Day One

Two are essential:

You insure your home - the building - and its contents as a matter of course. So it should be obvious that you also need to insure the house you are building.

Build insurance will cover your tools and equipment, the building as it progresses and you as an "Employer" whilst the various trademen are on site.

Think about it sensibly,  what if some disreputable chaps (aka robbing scoundrels) break in and nick all your tools - result damage to your home and the loss of pricey equipment and money you need for something else.  Worse what if some catastophe renders your build suitable only for demolition - add insult to injury, you will have to pay for the demolition......  All that money gone.  Insurance is not cheap, but it is far, far cheaper than dealing with possible consequences of not having any.

When you see a new house for sale on a development site, they all offer a warranty - most of you will recognise NHBC Warranty.  This is a ten years latent defects warranty issued by the insurer which can be claimed against in the instance of failure of some part of the build due to faulty materials - not workmanship.  For faulty workmanship, the chap who did the work is responsible.

Your warranty insurance depends upon a qualified surveyor making checks on your build at various stages, thus part of the cost of the insurance lies in the travel distance and time and hourly rate of a suitably qualified individual.  So it stands to reason that the cost of the Build Warranty can be reduced if it can be supported by a local professional.  

So although you may immediately be drawn to the big guns of NHBC and Zurich, search these online through Buildzone and similar.  A;sp check out the 10 year Warranty Insurances associated with your local authority Building Control (LABC)  and the independent Building Control services in your area.  You know it makes sense!

The Build Warranty is absolutely essential if you are likely to be selling your new home within 10 years of completion.  If you know you will not be moving on, there is an argument not to take it out.  If you have already started/completed your build, you can still take out a Latent Defects Warranty, but of course it will be more expensive than one taken out a the start as the insurers have no idea how or with what the house has been built.