>>>My wife seems to think that some kind of inhertance tax law stopping me from doing this
There are a lot of misunderstandings about Inheritance Tax ('IHT'). IHT is completely irrelevant if, when your mother passes away the value of her estate is less than £325,000. However, when calculating the value of her estate, any gift made within the past 7 years is included in the amount. If your mother, say, sold you a house worth £200,000 for just £1,000 then the tax man would treat that as a gift of £199,000, which would have to be included in the assessment of her estate. (Assuming that your mother hadn't made any other gifts in that tax year, or the previous one, the actual figure used would only be £193,000 as you can make a gift of up to £3000 per year tax free and you can carry over the allowance from one year to the next).
Further, if your father passed away leaving the house (or his share of it) solely to your mother, then she also gets
his £325,000 allowance, so there would be no IHT to pay if the total value of her estate (including any 'gifts' of the form outlined above) came to less than £625,000.
Note as well though that any 'gift with reservation' is exempt from the '7 year rule' that I've mentioned above. So if your mother 'gave' you her house (by way of a cheap sale) and continued to live in it [while not paying you the market rent for doing so] then the value of that gift [minus £6,000, as explained above] would always be included in the assessment of her estate, even if she lived for more than 7 years after making it.
See here for a full explanation of IHT:
http://www.hmrc.gov.uk/inheritancetax/
All of the foregoing relates ONLY to IHT. There are other rules in place relating to care fees, which mean that your mother's house can still be used to fund her care costs, even after she's (effectively) given it to you.
This link, relating to planned changes in the system, may also be of interest to you:
https://www.gov.uk/government/news/new-fairer-capped-funding-system-to-help-everyone-plan-for-the-cost-of-care