The important thing to remember here from the OP is that it's a NON-ENDORSABLE OFFENCE. Nothing has been put on their licence and it's a parking contravention.

Not quite sure why we have veered into 'convictions' as it's not one. It's also not a material fact as the information is not likely to affect the decision by a Underwriter.

Yes, quite rightly so that an insurer should decline for some convictions that are unspent. I've declined convictions for fraud, sexual offences including relating to a child, burglary etc. I've not declined on assault unless it's been serious with a substantial sentence otherwise I'd end up declining a fair percentage of the population lol!

Whilst I agree that UNLOCK can be sometimes helpful to some of it's members it's not entirely fair to say declining convictions is 'unsophisticated'. If one insurer decides not to write the business that's up to them. They don't want to carry a bad moral hazard. If someone has intent to steal something then that makes them a BIG risk to the insurer so your anecdote as to why theft would affect for motor insurance is quite ridiculous. A theft conviction airs dishonesty. It has been proven that the party has had the guilty mind to commit the act and also carried out that act. It's calculated. They decided to steal knowing that it's wrong and has consequences, no one else. What's to stop them being dishonest and fabricate or exaggerate the claim. I don't like thieves and I'd be more than happy to decline all quotes presented for this type of conviction. You have to remember that a judgment has passed to convict and therefore it's not a question of 'if'. It's theft. Plain and simple.

So the OP's case would have no place for UNLOCK. It's a simple parking ticket; and can you imagine if everyone had to declare those to an insurer!!! No. It wouldn't happen.