Hi Jo,
Cannot see a Boslam St on any of my 1850 maps, nearest is Boston St, Hulme. Looked in the Hulme Unfilmed and as you guessed the lower house numbers are missing.
I did find these in the 1855 directory
James Beevers, Shoemaker, 39 Piccadilly, house at 60 Mornington St, Chorlton on Medlock
Martha Beevers, Widow, 78 Bloom St, Portland St
Rebecca Beevers, Widow, 12 Stanley St, Salford
Hope this helps
Dave