If you can get access to this book, you may be surprised at the number of Newbury independent chapels listed therein:
Berkshire Religious Census 1851
Edited by Kate Tiller
Published by Berkshire Record Society in 2010
ISBN: 0 9548716 4 2
Description: This volume contains the text of the ecclesiastical census for Berkshire, and includes returns for 434 places of worship – 204 Anglican, 224 nonconformist and 6 Roman Catholic, providing a wide coverage of religious activity in the county in the mid-nineteenth century.
I, too, have an interest in the 'Brethren' meeting in 'Mr. Westells yard Northbrook Street', as I encountered a letter some years ago at Hampshire Record Office relating Stephen Leach's experiences in exchanges with Mr Westall in August 1846. Sadly, there is no further indication to which Mr Westall he was referring, but Francis and William - sons of Sarah WESTALL, widow of William senr - joined the Church of Jesus Christ of Latter-day Saints in 1849. In 1851 Alfred Brown submitted the Brethren's attendance numbers, and his household may be found at ref. HO107 1685 fol 216 page 34. However, I have not encountered any registers of membership.