Transferring our beneficial interest to a new property

My dad died several years ago. He and my mum owned their property - where mum still lives - as Tenants in Common. My dad left his 50% share of the house to me and my three siblings in his will; my mum has a Life Interest in the house which means she can live in it as long as she wishes. I understand that dad's will means that I and my three siblings have "a beneficial interest" in the property.

My mum now wishes to sell the property and move to a new property. Let's assume the current property is worth £100k so that mum's share of the sale proceeds is £50k and the siblings' share is also £50k.

We  siblings do not wish to "liquidate" our £50k share of the proceeds. Instead, we wish the full £100k to be used to purchase the new property.

Each of the siblings already owns a property, We do not want to become joint owners of the new property as we understand that we may thereby become liable for Capital Gains Tax or "second property" Stamp Duty. 

Instead, we would like mum to be registered as the sole owner and for us to, in effect, transfer our "underlying" beneficial interest to the new property.  We only wish to realise our inheritance from dad (and mum) when the new property is sold upon mum's death.

Is a transfer of our beneficial interest possible? If so, how can this be achieved? Will this mean we are not subject to the aforementioned CGT and SDLT or any other tax? (We assume the proceeds from the eventual sale of the new property will be classed as an inheritance and that beneficiaries are not subject to tax.) 

Thank you.

Yvonne - we register the legal ownership so if the property is sold and a new one bought in Mum's sole name she will be the sole legal owner. 
We don't register beneficial ownerships but they can be protected in the same way as for example they presumably protected the TIC/trust they created re shares etc, and which you refer to, by registering a form A restriction. 
What you are seeking to achieve does not as a result really involve ourselves and I'd recommend seeking legal advice as to how best achieve what you want to achieve, new will(s) and or trust arrangement.
We don't deal with CGT/SDLT/taxes so I would recommend widening your research online or contacting HMRC as appropriate. Online forums such as Money Saving Expert can be very useful resources re such subjects although specific and personal legal advice is always recommended