Hi Colin,
thanks for the modern photos/link, I've not seen those before. I only know it from older photos and suchlike, hope this additional info is of interest;

This website gives a little more history and confirms it is, as you say, a Baptist Chapel dating from about 1846.
http://churchdb.gukutils.org.uk/GLS798.php

The following old photos show that it's appearance hasn't changed much, particularly the impressive entrance doorway.... here is Longhope Zion School's class of 1928 outside the Church entrance.
http://forest-of-dean.net/gallery/longhope/pages/page_2.html

Longhope's first school was C of E, built in 1829 in the village centre next to All Saints Church and Rectory. The Zion School was founded only a few years later, over a mile out of the village up Hope's Hill towards Little London. Whether or not this school was first held within the Chapel, rather than the later schoolroom next door, is unclear, but one reference book states the Schoolroom "behind the Chapel had to be enlarged in 1893". The Zion school room was still active when this history was written in 1986.
http://www.bbc.co.uk/history/domesday/dblock/GB-368000-216000/page/17

The school was funded by Edward Goff, a local benefactor and devout Christian, he's described in more detail in the interesting Gorsley Village website, http://www.gorsley.com/school.html

Here's an older photo of Zion Chapel and neighbouring "Institute" (was this the schoolroom ?). This postcard image was one of the "Bradley's series" of postcards; my Great Great Aunt Elizabeth Wright nee Bradley ran Bradley's Stores in Longhope c1905-1920s, this and other cards were sold by her, many if not all the photos were taken by prolific Longhope photographer Harry Beard, sometimes printed by the wellknown card manufacturerers Tilleys of Ledbury, who's colour images can be found within this site's Gallery.
http://www.oldukphotos.com/graphics/England%20Photos/Gloucestershire,%20Longhope,%20Zio...

Zion Hill school became known as Hope's Hill Primary School later in the C20th, it's mentioned at base of this Longhope village website page. I think this normally excellent website is in error where the top section suggests the Zion School is post-1911.
http://www.longhopevillage.co.uk/history/Schools/

Zion/Hope's Hill School was amalgamated with Longhope Church of England School in 2001, within a new building in the centre of the village near the Recreation Ground, now called "Hopes Brook C of E Primary School".

NB: I'll try to update this post, and maybe also the Longhope Village website, when I next see my mother's copy of the British History book for Longhope. I also plan to upload more images of Longhope life from Harry Beard's camera, including a clearer one of the above-mentioned postcard.