Personal injury claim didn't acknowledge Thin Skull rule? What now?

[Buel10]

Hi all.
On Thursday, a barrister acting on behalf on my trade union law firm represented my personal injury claim against my former employer in a local court. In the email from the law firm, they stated 'The judge noted the bracket was unhelpfully wide and that the Claimant's injury was ultimately an exacerbation of a pre-existing symptoms'.
I replied to them that they / the barrister hadn't used the 'Thin skull rule' (essentially, you take your victim as you find them, more below) that I had agreed with the previous claims handler months ago should be used if the defendants' solicitors tried this get-out. They replied with 'you cannot appeal the judge's decision, as you were informed prior to the hearing the judge's decision is final and not something we would appeal further'. My question here is can i appeal this, and what can I do, legally, if they did not use this extremely valid argument?
*https://en.wikipedia.org/wiki/Eggshell_skull

[Buel10]

Bumpy Bump, anyone?

[des8]

You will find it extremely difficult to appeal the judgement.
Your better course of action would probably be suing your barrister for Professional negligence.
However that is not as easy as it sounds.
You need to show the barrister owed you a duty of care; that he breached that duty and it caused you to suffer a loss.
The difficult part is proving he breached the duty of care.
Proving your barrister not using a particular argument caused the loss of your case is extremely difficult as any number of factors bring about a judge's conclusion.
*