From the UK AIP:
ENR 1.1.3 — GENERAL FLIGHT PROCEDURES
4.2.4.1 A flight experiencing communication failure in IMC shall:
(f)...When practical, pilots should take account of visual landing aids and
keep watch for instructions that may be issued by visual signals from the ground.
(g) If communications failure occurs during an approach directed by radar, continue visually...
In answer to the original question, it seems that if communication failure occurs on short final, then to land without having received a clearance is the correct thing to do. (My bold)
G W-H