If the job ceases to exist, the job is redundant. It is the duty of the employer to work with the employees without roles following a redundancy situation to seek to redeploy within but the job has to be broadly similar, or the employee has to be voluntarily willing to accept an alternative role on lesser terms (salary or whatever). Offering a compulsion but with reduced salary doesn't sound like broadly similar.
That's the legal version, but in a highly manipulated like the NHS, deals may have been done with unions that have agreed different protocols (that give the employers even less room for manouvre - like putting folks in a redeployment pool for months on end, for example, waiting for that elusive equivalent job to turn up).
Since you work in the NHS, you'd presumably know about these sort of arrnagements.