(I assume that Anglian water did the analysis you suggest and came to the same conclusion as @dixi188 ).
Anglian water have planned, and have proceeded with a monsterous new 'large pipeline' project from the top end of Lincolnshire to Essex.
It has been interesting to watch it develop.
Total length is ~500Km of which over 170 Km have already been installed (For comparison the GU proposal is only 135Km)
We’re creating a new drinking water grid for the East of England.
It is one of Europe’s biggest environmental projects and the most important in Anglian Water's history.
Once complete, hundreds of kilometres of underground, large-diameter, interconnecting pipelines will stretch from North Lincolnshire to Essex. They will be supported by new infrastructure such as pumping stations and storage reservoirs along the route to bring water to customer’s taps.