I have phonak rechargeables in the UK, here they told me that never "service" a hearing aid, merely replace under the "lifetime" warranty.
I very much doubt you will get it serviced, sorry!
You should look up "Deprivation of Assetts"
Your mum theoretcially cannot gift you her house and contiune to benefit from living in it, I guess its like saying "You cant have your cake and eat it"
See:
https://www.ageuk.org.uk/information-advice/care/paying-for-care/paying-for-a-care-home/deprivation-of-assets/#skipToContent
Good luck.
Paul