The tax position is fairly clear on this –
The value of the property crystallises on the date of your mum’s death for Inheritance tax purposes – as the estate is likely to be below the inheritance tax threshold tax payable will be nil.
At any subsequent disposal of the property you will be liable for capital gains tax on the difference between the price that you sell for and the value that you inherited at.
So say you inherit at £200K value and Sell for £220K – capital gain is £20K. Your share is a third £6,666 which is your personal capital gain. This is less than your capital gains allowance for the year and the tax payable is again nil.
Capital gains above the yearly allowance are taxed at 18%.
If you need help with probate drop me a line e-mail in profile. It is what I do for a living.
Nick.