Flooding From Neighbour.

[SparklyKid]

The house behind us has erected a huge garage which almost touches our fence.
We live on the edge of a flood plain.

The garage foundations seem to have disrupted an underground water course causing flooding on our drive.

Who do I approach ?

Planning dept, north west water, united utilities or the environment agency.

[davebro]

also a good place to shove noisy teens out of the way!

[The Builder]

How can you be sure it's underground water Sparky?
Water is well-known for turning up some way from its source.

You may well be right though. Excavations might well have disturbed a spring. It's not uncommon.
To try and answer your original question, my first shot would be to get in touch with the Building Control inspector who oversaw the build. He'll come out and take a look.
Then, Environment Agency.
We shouldn't hold our breath though.

The sad thing is, these things often come down to ... lawyers.
It would then probably take ages; cost a fortune; and maybe get nowhere.
Find the Building Inspector first.

[SparklyKid]

Hi Builder. We live on a residential Country Park and pay a site fee.
The park owners, on whose the land is affected, are going to investigate.

When the garage foundations were dug out, about 2 feet deep, within a few days they were full to the brim with water.
I shall leave it to the site owners to attempt a resolve. Thanks for your advice.