I have contacted several different lawyers and OISC accredited legal professional on the below matter each have given a different response

using expired b1 for ILR set M

The Immigration rules (Immigration Rules Appendix Koll) says you cant use
however

Knowledge of language and life in the UK Version 20.0 ( says you can(

what is correct

Areas of Expertise: 

Public Answer: 

Dear Sir/Madam,

Many thanks for your questions.

You may be able to rely on your expired B1 certificate if you used it in a previous immigration application

Our immigration solicitors will contact you shortly.

[This question has been successfully answered by our lawyers in a private e-mail]