Although when I raised it with the GP during the last hospital stay they said it wasn't anything to do with them while mum is in hospital.
If it's regarding the standard CHC checklist assessment they're correct. A persons true needs can be masked whilst in a hospital environment, especially the elderly, so it's best to have the assessment done when they have returned home and are more settled.
You said previously:
When I asked the social worker he refused to even consider it for mum.
Was this a hospital social worker or a local authority social worker? If the latter then what was his rationale for refusing to do a checklist assessment? If it is a hospital social worker he may want to wait until mum is back home and settled.
A checklist assessment can be refused if it is obvious there are no significant needs which would warrant one, but as a positive assessment has already been completed previously by a discharge nurse it would indicate that the social worker (if local authority) has no reason to deny one now unless your mums needs have improved significantly. Everyone is entitled to have an assessment so if it were me I would be telling him I want one arranged and if he refuses then I would want his reasons why put in writing. Also, make it clear you want to be part of the assessment process as your mum has a right to representation during the process.
It may be helpful to go over the checklist used during the assessment and score your mums needs as you see them. During the actual assessment you can refer to what you have scored each domain and any notes you have made as to the reasons why and then use that should the person doing the assessment want to give a lower score than yourself.
If your mum is still in hospital then now is not the right time to do a checklist assessment - as your mum has a terminal illness I would probably be pushing for CHC Fast-track. A Fast-track application can be done whilst she is still in hospital (I think?).