Altruistic Surrogacy is legal in the UK if the correct procedures are followed, but commercial Surrogacy is not.
It is a criminal offence:
To advertise that you are looking for a surrogate or willing to act as a surrogate;
For third parties to advertise that they facilitate surrogacy (although there are some exemptions for not-for-profit organisations);
For third parties to negotiate the terms of a surrogacy agreement for any payment (for example a solicitor cannot assist with agreeing the terms).
Furthermore, Intended Parents are only allowed to pay the surrogates ‘reasonable expenses.’
If you use a surrogate, they will be the child’s legal parent at birth. If the surrogate is married or in a civil partnership, their spouse or civil partner will be the child’s second parent at birth, unless they did not give their permission. Legal parenthood can be transferred by parental order or adoption after the child is born.
If there is disagreement about who the child’s legal parents should be, the courts will decide based on the best interests of the child.
Often the Intended Parents and Surrogate will enter into a Surrogacy Agreement. Such an agreement is helpful in setting all parties understanding and agreement on a range of issues.  A Surrogacy Agreement is a non-legally binding statement of intention about how the arrangement will work and the commitment that each party is making to the other in advance of the surrogacy commencing, to ensure there is effective communication and mutual understanding between the Intended Parents and Surrogate. It is vital to note that a Surrogacy Agreement it is not legally enforceable or binding on the Court in this jurisdiction.