Sorry to hear that. The silver lining is that you are only required to pay the original £100 charge and the fixed hearing fee. Consider how much they were trying to get from you, you can see that it is always worthwhile defending a claim as they will rarely get the total amount they are claiming.
It has definitely cost them more than they will have recovered as they sent a representative to the hearing. That is likely to have cost them at least several hundred £ which they cannot recover. They have not recovered the £27 trial fee either. There is some Schadenfreude to be had for that. Hopefully, you have had a valuable life lesson on how the civil courts handle disputes.
As long as the £135 judgment is paid in full within 30 days, there is no record of this on your credit file. It is completely expunged from the record.
You appear to be confusing some terminology. You are the Defendant. Excel Parking are the Claimant.
Did you not point out that you were unable to properly defend the claim as the claimants PoC were defective and did not adequately comply with CPR 16.4?
Whilst you did raise the defective PoC/“ambush by WS” issues in your WS, the judge indicated the factual basis (payment attempts/system failure) should have been pleaded in the Defence, not only developed later in the WS/SWS. That’s a very common judicial stance in small claims: It's know as "Judge Bingo" and depending on which judge you get, they’ll often tolerate poor PoC but still expect the Defence to state the core factual case, then use the WS to evidence it. A different judge would likely have judged the other way.