This sounds like an absolute shit scenario. Sorry mate.
I've just been asking around and I hear there's a bit of a rep with ML that I wasn't aware of either.
Not that it's any help now, I have a recommendation of BMR in Crawley.
As to whether you want to spend more money on it, that's another question.
If you're less guilty minded than I am, I'd say get it to a point there's no errors and absolutely fuck it off ASAP. Even if it's to We Buy Any Car so you don't have to look the buyer in the eye.
If you can afford to, perhaps speak to this BMR place to see what's the most cost effective way of getting it all sorted.
I feel for you dude, I've been there before, and shit service from supposed specialists is an absolute wounder.