As tenants in common the clause on your title deeds is quite normal in the situation you describe, the upper limit of capital is £23,250 over which you are expected to fund the cost of care fees yourself, the lower limit is £14,250 below which you do not necessarily make any contribution. With the upper limit being so low almost anyone owning a house would be required to pay, there is no law which says you have to sell your home to pay for care fees but for many people this is the only possibility, which can seem very unfair.
Anyone in this position should speak to a solicitor over setting up a trust, which can also have advantages with inheritance tax, it could be money well spent.
Yes Martin, a court can override the clause and grant an order for sale