Can a letter of sponsorship from Nigeria suffice for a proof of fund?
It depends who is asking for proof of funds and for what purpose. If it is for the Student visa, a letter from an Official Financial Sponsor showing they will meet your costs is acceptable instead of evidence of funds in your own name. See Immigration Rules: Appendix Student, paragraph ST 12.6: ST 12.6. Unless the applicant is relying on a student loan or on official financial sponsorship such as an award from a Government or international scholarship agency, they must show that they have held the required level of funds for a 28-day period and as specified in Appendix Finance. Official financial sponsorship is defined in Immigration Rules Appendix Finance, paragraph FIN 8.3(b) FIN 8.3. (b) [] an official financial sponsor [] must be Her Majestys Government, the applicants national government, the British Council or any international organisation, international company, university or Independent School