I drive past here quite often and can see what looks like a summerhouse on top of the hill coming from Barnston. Just a bit curious.
<https://maps.google.co.uk/?ie=UTF8&ll=53.351243,-3.085163&spn=0.007621,0.013797&t=h&z=16&vpsrc=6>

Can't get the link to work :((

not the only one?

Managed to get the map but can't put it up on here for some reason. what are you looking at on the map ?

If it's that square lighter coloured area, it is private property belonging to the water company.

Works for me..
https://www.google.co.uk/maps/@53.351243,-3.085163,738m/data=!3m1!1e3
and granny right

Vent / access for the underground reservoir?

http://binged.it/1i18xK3

Gibbo is correct.

Thanks everyone.