Could you try your local social services or council website to see if there are any carer support services in the area for mum?
Social services can offer an assessment if your dad's functioning does deteriorate, you can contact teams directly to request same.
If your dads behaviour became problematic, you could ask his GP to rule out any acute physical cause for the change such as UTI, constipation, chest infection etc in the first instance, and if needed ask GP for referral to community mental health team for older people for further assessment and any ongoing monitoring/treatment.
I would have suggested visiting the alzheimers society website as they have lots of information on different dementias, how to cope, what to do, who to contact but you have said it wasn't a dementia. Really the diagnosing consultant should have given you some local contacts IMO.