The "bible" - CRAG - which Social Services have to (or should!) abide by is here:
http://www.dh.gov.uk/...alasset/dh_115533.pdf
Go to section 7, starting on page 41. 7.003 seems to me to make it clear that if you are over 60 when your mother has to go into care the bungalow has to be disregarded in working out your mother's entitlement to Social services help with care home fees. Further on (about 7.019 I think), there is information about the value which can be attributed to a share of a jointly owned property. This says that it could be that the share would be very little, or even nil, because there would be no willing buyer for such a share.
I do not see how deprivation of assets could come into this, as you are a joint owner of the bungalow.
Despite all this, you could still have to stand your ground with Social Services if the time comes, using whatever up to date version of CRAG is applicable at that time. Incidentally, it might be an idea for you not to move in until you are 60.