@SWP's back
I'm not going to check over all the pages to see if this was answered already, but you were asking for a source on the claim any possible appeal goes to the high court rather than to CAS. I'm not a lawyer or anything, and have only skimmed PL rules, but this could be the relevant section:
Agreement to Arbitrate
X.2. Membership of the League shall constitute an agreement in writing between the League and each Club, between the League and each Director of each Club and between each Club for the purposes of section 5 of the Act in the following terms:
X.2.1. to submit all disputes which arise between them (including in the case of a Relegated Club any dispute between it and a Club or the League, the cause of action of which arose while the Relegated Club was a member of the League), whether arising out of these Rules or otherwise, to final and binding arbitration in accordance with the provisions of the Act and this Section of these Rules;
X.2.2. that the seat of each such arbitration shall be in England and Wales;
X.2.3. that the issues in each such arbitration shall be decided in accordance with English law; and
X.2.4. that no other system or mode of arbitration will be invoked to resolve any such dispute.