We are looking at LHA being paid direct to landlords from the tenant's bank account and wondered whether a landlord include a clause in the tenancy agreement stipulating that payment of rent must be by direct debit.

Any help greatly appreciated.

I'm not convinced that a L/L can stipulate to a LA that HB must be paid in any particular manner, but an LA must have regard to a couple of issues. The relevant reg is HBR 91.

The LA is required to firstly consider the times and frequency as to when liability arises. So, no relevance to the METHOD of payments.

Next; the LA has to consider the reasonable needs and convenience of the person entitled (i.e. the claimant).

Based on the above, I can't see that a L/L could insist on payment by direct debit.

Housing law on this (case law, not statute) is that a landlord can put a clause in the tenancy agreement stating that he wants the rent paid in a particular way by the tenant. He can also make such an agreement verbally. The method of payment the landlord asks for can't breach the Unfair Contract Terms Act, other than this there is no particular restriction. But if the landlord has previously agreed to accept more than one method of payment (eg, has said he will accept cash or cheque) the courts would consider it unreasonable for him to then restrict it to one method only. This is because he is trying to unilaterally change a mutual agreement he has made with the tenant.
You might be successful in telling new tenants they must pay their rent by standing order. Existing tenants who have previously paid in other ways would have the right to object. And it will be a non-starter (naturally!) for tenants who have a post office account but no bank account.
Landlords can't insist on the local authority paying them in a certain way because their contract is with the tenant, not the local authority.