Good luck with Old Oscott Lyn!
On this site there're details of Beech Tree Cottages in 1921 when they were all auctioned off in 3 lots.
https://www.perrybarrbeyond.pwp.blueyonder.co.uk/07 - Baylis - Bellairs.htm
It looks like there was once 14 cottages. As a separate lot, the PO was listed as a shop and had land attached. I expect some were demolished in the process of developing Kingstanding in the 1930s and the ones next to the PO in the 1960s photo would have been demolished maybe in the 1970s. I've extracted the auction info from the site:
Description from the Auction Sale Catalogue from the Perry Barr Estate, Birmingham 1921 Holly Lane, Erdington In the Parish of Perry Barr, in the County of Warwick, Staffordshire
BEECH TREE COTTAGES
A block of Seven Freehold Cottages With gardens, situate & known as 9, 10, 11, 12, 13, & 15. Brick built & tiled, each with 2 bedrooms, living room, scullery etc. Companys water to each. All let & producing gross total rent of £88. 8s. 0d per annum.
No 9 Mr George Hartle £13. 00. 00
No 10 Mr E Miles £13. 00. 00
No 11 Mr H W Compton £13. 00. 00
No 12 Mr A L Wells £11. 14. 00
No 13 Mrs Summer. £13. 00. 00
No 14 Mr A L Wells. £11. 14. 00
No 15 Mr Lawrence £13. 00. 00
Tithe Rent Charge 5 shillings per annum
BEECH TREE COTTAGES
A block of Six Freehold Cottages With gardens, situate and known as 2, 3, 5, 6, 7 & 8
Built of brick with tiled roofs. Nos: 2, 3 and 5 each contain: - four bedrooms, living room, kitchen, scullery etc. Nos 6 and 7 each contain: - two bedrooms, living rooms, scullery etc., and No 8 contains, 3 bedrooms, kitchen etc. Companys water to each. All let & producing a gross total rent of per £78. 0s 0d per annum
No 2 Mr M Carneye £13. 00. 00
No 3 Mr A L Well £11. 14. 00
No 5 Mr A L Wells £11. 14s. 00
No 6 Mr E Curtis £13 00. 00
No 7 Mr Clayton. £15. 12. 00
No 8 Mr J Curtiss. £13. 00 00
Tithe Rent Charge 5 shillings per annum
BEECH TREE COTTAGES
Known as No 4 Brick built and tiled. Three bedrooms, Attic, Small Shop, Sitting room, kitchen etc. Companys water. Included in this lot are the two excellent enclosures of Arable Lane in the rear, being Nos. 257 and 248 on plan, and having an area of nearly: FIVE AND A QUARTER ACRES Let to Mr. J Ryan on a yearly tenancy at a rent of £27. 10s 0d per annum, tenant paying rates. Tithe Rent Charge 4 shillings 5d per annum