My question is, what is required under UK law to assign the benefit of a debt or small contract, to a third party. Although it relates to an actual dispute, the question itself is simply about legal process and facts of law - no advice is sought or needed beyond that posed in the question. Therefore I am also abstracting the question completely, to make it as widely applicable as possible.
A, B and C are private UK based individuals.
A is due money under a contract with B. A has performed their part of the contract so the only contractual matter outstanding is A receiving their money from B. For personal reasons, A now wishes their friend C to become the sole beneficiary thenceforce, so that C can claim from B the monies or any other contractual benefits previously due to A, or if needed, C can sue B for their non-payment/non-delivery (if that happens).
The motive for this is partly, that C will give A a sum of money, and will subsequently have full rights to receive, collect and enforce the debt owed by B in exchange.
Can A and C enter into such an agreement of assignment without seeking B's consent, and what form must such an agreement take to be legally binding?
Note: It is assumed that the contract does not explicitly forbid this, nor is the contract related to real property or a lease/tenancy, or a business. The debt/benefit is small, under £500 in value, and relates to a deposit that A previously paid B and which B now must repay to A.