As built the northern stations had 2 escalators flanking a staircase.
Seven Sisters had a second entrance which had a double escalator without stairs. They also saved money by not cladding the tunnel ceilings at these. The bottom of these escalators are all at different parts of platform to spread passengers along the train.
Finsbury Park took over existing arrangement, Highbury and Islington kept the North City line arrangement (but added pair of tunnels), from memory the escalators that connected to North London Line (now Overground) were added with GLC funding later.
The middle stations Kings Cross, Green Park, Victoria were built with 3 escalators (Green Park also had an upper flight with 2 to ticket Hall)
Euston had pairs of two to a middle concourse that allowed connections to all the Northern line platforms, then bank of 3 to ticket Hall, I think there was only 2 to BR concourse (but a direct link to the suburban platforms at tube ticket hall level)
Warren Street had a middle level to connect to Northern, but to save money only 5 escalators plus stairway were installed.
Oxford Circus had new platforms outside the Bakerloo ones, there were additional single shaft up escalators to the old Central- Bakerloo ticket Hall (which became exit only). The new entrance Hall under the circus had 3 new pairs of escalators to each pair of platforms. Intermediate concourses exist so the down escalators are positioned away from the exiting part of platforms.
The Southern stations had 2 flanking a staircase, Brixton gained one later and I think Vauxhall also gained a third escalator around the time the bus station was rebuilt (not sure about this).