I disagree with your solicitor.
I think you have an excellent chance of succeeding with the Inheritance Act Claim - but less chance of getting an injunction
There is no Tenancy and you have no legal right to live in the property - which makes you an Excluded Occupier - or will do when proper notice is served after the Probate has been granted.
This is why I asked if the person who advised you of the opposite had explained the basis for the advice!
I am of course happy to opt out so see if someone else can come up with a reasonable justification for such a claim.
However I do believe you have an excellent chance of succeeding in either an Inheritance Act Claim - Or potentially a claim in Proprietary Estoppel
The estoppel case will be on the basis that your father promised that you would be safely housed if you can=me and looked after him and you acted on that basis
You can read more about Inheritance Act Claims here
Within an application for either claim you could certainly apply for an Order allowing you to remain in the property whilst the case is ongoing.
Realistically I do not think you and your siblings will receive all the estate so negotiations with Nora will be necessary
Please ask if you need further details (or would like me to opt out!)