Ok from another site:-
f you are paying by cash we do not require any identity for orders under £5,000 in a single transaction or less than £10,000 in multiple transactions over a 12 month period.
For orders in excess of these limits we are required to keep identification to comply with HM Revenue and Customs regulations. We need one piece of photographic identity (passport or drivers licence) and one household bill to prove your address (utility bills, bank statements, credit card statements). Certified copies must be signed by an authority figure (Lawyer, Accountant, Doctor, Policeman) or you can get the copies certified at the post office for a small fee. If this type of ID is required a member of the team will contact you to explain the process.