Newbury valve? Vented hot water cylinder

Hi all
Can anyone help me find a valve (I think it's called a Newbury valve) that replaces the coupling on top of the hot water cylinder, drawing the hot water from a few inches below the surface, but still allowing venting to the loft tank. I need this as every time we turn the hot water on in the bathroom it spits at us, just once, but fairly forcefully and is very annoying. This only happens when we have the pump switched on (inline Grunfos - the proper one not the central heating pump), and we don't notice it downstairs in the kitchen at all.
Thanks to anyone that tell me what to look for. Plumb Centre staff just looked blank and sucked their thumbs when I explained what I wanted. Not much use there.

Surrey flange ??

That's the one. Many thanks. Guess I was was a few miles out. Memory drifting perhaps.
Thanks again for such a quick response.

Your welcome

Surrey, Warix and Danzey flanges all do the same job slightly differently.

Plumb Centre in terms of staff normally equates to dumb centre, sadly. Try a local independant merchant; Plumbstop, Swindon Plb Supps.