From UK CAA Information Notice 2015/009:
Important Note:
Applicants for and holders of the IMC Rating or IR(R) must maintain a PPL(A) or higher aeroplane licence. A LAPL(A) is not sufficient. Part-FCL does not permit any kind of IR (Modular, Competency-Based Modular or En-route) to be added to a LAPL(A). The LAPL(A) is designed to be a VFR-only licence and the training and skill test for the LAPL(A) reflect this.