Which vat scheme to use?

Dear Colleagues,

I've taken on a new client, small ltd co. They are involved in collecting recyclable waste from small firms, often free of charge, cleaning and recycling the items, e.g. 1 ton tote bins and selling them on at a profit.  Due to the nature of their business, they have a number of sales were they are paid directly in cash, also, 2 of the clients they have which are repeat fee clients are currently imposing 60day payment terms on their invoices- so cashflow could be an issue.  Given this info, what VAT scheme would you advise this co. to sign up to?