Agree with the above (from respected HR practitioners).
But it doesn't stop you questioning it with the HR team at your works. This can sometimes be an issue for those working in different locations including London, where expensive locations are impossible to finance within the allowance. Go gently, rather than guns blazing, and suggest they find you the accommodation within budget. Sometimes this tack then degenerates into 'that place is unsuitable to sleep a cat'. Much depends on the value they place on you and your flexibility as a valued employee to them.