westernone,
A contract does not have to be in writing. It can be writen, verbal or Implied.
"- booking deposit paid by cheque, (Why?) to hold the house for one week "
(The contract would seem to be: your friend would pay €1,000 in return for the Landlord 'holding' the property for one week. If property was held for one week and payment was made then that contract was completed.)
"whilst away on business, pending signing of lease
- no contract exchanged
- no documentation ..receipt or otherwise exchanged"
It would probably be better for your friend to take the view that she wanted that period of time to consider wheter or not she would take up the lease. IMHO, as you spell it out, there was in fact a further contract to lease the property. The landlord cold seek to enforce this contract. This was an implied contract. But what would the 'Terms' of the contract be? Well "... I would see that the deposit was an indication in good faith that my friend intended to lease the house." if your friend, or the landlord's agent, made any reference to a period (say min. 12 months) then the contract would be to lease the property for the quoted rent and for the quoted period. Your friend could be bound to pay 12 months rent.
I'd suggest it is highly unlikely that the landlord would pursue this - it would be subject to alot of heresay, although your friend would have to deny, under oath, the terms discussed. The landlord would have the benefit of a witness - 'the wellknown agency'. I would suspect if it was pursued the landlord would have to show Loss and any claim would be limited to that loss.
Re: PRTB - In the circumstances the Tenancy was not registered with PRTB. The Landlord and Tenant are required to sign a form PRTB1.