You really should try switching to the velours after fussing with the pleathers so long. For $10, EQ or not, they are the most balanced, the least "ringy", and the treble is less "peaky". You lose that touch of "warmth" that the pleathers seem to give, but its worth it, IMO. I'm done with the pleathers modded or not - they are just sub-optimal.
199 pounds is what, $260 USD? That's pushing it considering brand new is now $300. I'd think it'd be lucky to see $200. I'm not sinking any more into mine either (though I would go for a new cable). But if I could sell them + my Senns for about $200-$300 I suppose that would be good enough despite the heavy losses I'd be taking. It isn't clear I could stick with Hifiman at this point - they've sketched me out with the short warranty and somewhat obvious shortcomings (cables coming apart, and lousy SMC connectors that are an unnecessary PITA). Unclear if any of that is going away with the new generation.
$$$ compared to £££ is not really relevant in the UK because you cannot import things without paying postage, tax and duty, so £199 is about the same as $199 dollars US.