It is quite likely that you will not accept the PIAB award and your case could run on for a number of years.
Your Solicitor should not be looking for money from you at this stage unless there is an issue with Liability and he/she feels that there may be an issue with receiving a settlement award however in that instance your claim should not be with PIAB as the other side would have rejected to have it assessed by PIAB.
In answer to your query, there is a possibility that you may get a loan from the Credit Union if you provide an Undertaking from your Solicitor to clear the loan immediately on your behalf once settlement sums are received by him/her for your accident. Once the settlement sums are recovered your Solicitor wold issue payment to the Credit Union before provdsing you with the remainder of the settlement.
Firstly, you will need to query if your local Credit Union provides this option and then you will need to see if your Solicitor is prepared to give the Undertaking.
Alternatively if Liability is not an issue, you could ask your Solicitor to request an Interim Payment from the Defendant's Insurance Company to aid your recovery. It would be in their best interest to provide you with the payment to enable your to recover more quickly. Sums in the region of €5,000 are often sought in more severe cases, which is the catagory your case would be listed in.
HTH