There is a lot to be said for letting PIAB to assess your claim. QD will be trying everything to buy u off for less than your claim is worth. At least the PIAB is independent.
If you engage a Solicitor from the outset, your Solicitor will be able to secure evidence and take steps to ensure a successful outcome if the matter is thrown out of PIAB. In court, you might regret not having secured vital evidence, which might not be obtainable at the time the matter is released from PIAB.
A Solicitor will always take on a case provided it is a good case and the client has not succeeded in making a mess of it (eg. not suing all parties who might have a liability)