Solicitors will generally have a non-interest bearing current account and an interest bearing deposit account for client funds. Absent specific arrangement to the contrary, the client is entitled to receive the 'demand deposit' rate on his\her funds, but only if the sum involved exceeds €100. The demand deposit rate is very low, but then the client money is indeed available on demand so that is probably fair enough.
In the normal course of things, the funds should have been paid to the client by now. If there was just one mortgage to be redeemed and nothing else outstanding at completion, client is right to be irritated. However, it is regrettably common that there will be things outstanding at completion; For example:
a. Evidence that refuse charges were paid up to date,
b. Evidence that NPPR charge is paid or is not payable. ( the new 'second house tax)
c. Evidence of discharge of inheritance tax ( if applicable)
d. BER certificate
e. If mortgage was with a bank with whom client also had\has current account overdraft, personal loans(s) or credit card, confirmation that the bank do not require these to be cleared out of sale proceeds
And so on
It is possible that the solicitor completed the sale on the basis of undertaking to furnish one or more such outstanding items. It is also possible that solicitor expected to have the outstanding item(s) within a day or two and that this has turned into a week or two. Irritating certainly, but not necessarily the solicitor's fault.
Bottom line - if there is no actual reason for the delay in finalising things, client should get stroppy. But based on the limited facts given, we cannot rule out the possibility that there is a valid reason for the delay.