You have specified the shell width as 70mm.
This is a problem on the Raleigh bikes, which as far as I know, never use an Italian threading (which is also a 70mm width).
A normal British bottom bracket shell is 68mm.
The 70mm indicates that the bottom bracket uses Raleigh's own thread pitch for which replacements are no longer available. It is possible, though not a fantastic option, to re cut the threads with standard BSC/British thread pitch though this weakens the thread somewhat, and will give a small centreline error with your new cranks on a square taper BB as the shell is 2mm wider than it should be. You can't install most threadless bottom brackets as the thread engagement is usually not enough over the 70mm shell. You could also see about having the shell reamed out and cut with Italian threads (for which the 70mm width would be correct).
No easy answers, sorry.
This page provides more detail so you can compare what you've got in front of you and see if I'm right.
Right through the 1990s, the bikes built at the mighty Nottingham Factory were made to Raleigh proprietary dimensions. Since Raleigh made virtually every part of these bikes, there was no compelling need to match standards used by other manufacturers
If you re-measure and find the shell is actually 68mm, that changes the situation!