I am not a lawyer, and I am assuming trusts in the UK work similar to the way they work in the US...
A trust is a legally recognized entity that can act in business transactions much the same way as a person would (own real property, a business, insurance, investments, etc.). The short answer is the trust is the owner of the property.
The trust is established by a Grantor who "funds" the trust by transferring ownership of items from him or herself (or itself, if another trust or business entity like a corporation) to the trust.
A Trustee is appointed (usually by the Grantor) to manage the trust according to the conditions and terms specified in the trust. A Trustee would be failing in their responsibility (their fiduciary duty) if they do not act in accordance with the purposes of the trust. (Some trusts are written better than others, and there may or may not be room for broad interpretation of the purposes of the trust.)
The trust is established to provide some benefit to the Beneficiary. The beneficiary can be anyone or anything, including another trust.
In the US, a living trust is commonly used as an estate planning tool, where the Grantor, Trustee, and Beneficiary are the same person(s). At some point, due to health or other reasons, a new trustee can be appointed. Since the trust is a separate entity from the grantor and trustee, and it owns the assets, it can survive the death of the grantor, which makes it an attractive way to avoid having to probate the entire estate. A good living trust will have instructions for the Trustee on what to do with the assets upon the death of the Grantor(s).