I can see what you wrote. You said that a chain and lock has to be approved by your insurance company. Then you quote 3 cycle-specific companies as proof.
A colleague at work had his bike nicked from outside the office a couple of months back. His insurance company didn't ask what lock he used before they sent the cheque out.
You said don't buy a cheap lock for a decent bike. That's too vague for someone reading this who wants advice. A cheap lock on a decent bike can be fine. Our police will sell you a silver rated lock for £5. That's very cheap, and a pretty good lock. I know, as I've got two. I've already said that I got my gold rated lock for £30. A decent bike can be had for £300, and arguably 50% less than that.
Your average cyclist would be wasting his/her money going to a cycle-specific insurance company. Yes, they need to make sure of cover before taking out insurance, but that's the case for any insurance cover. Let's not suggest that people have to pay over the odds when they don't. Or confusing people by suggesting that a decent bike is one that cost the same amount as you paid. That's where we've been before.
Point 1. Cycle specific insurers provide on-line the fact that specific STANDARD of locks is required. House insurers do not, but they COULD still require such standard of lock to be used. YOU MUST CHECK.
Point 2. Colleague at work. Good for him. I would still check, and advise others to as well though.
Point 3. cost and being vague. Sorry.. If you buy a bike valued between £50 and £100, spend X amount, if between £100 and £200, spend Y, and if between....etc.
A decent lock is either Silver standard for cheaper bikes, or Gold standard for more costly ones, and those not wanting to lose their bike like me should use at least 2 Gold standard locks of different types. ie. one D-Lock and one Cable or Chain lock.
Point 4. Again with the cycle specific insurance. NEVER NEVER SAID anyone should get cycle specific insurance. I used them as an example to show the standard of lock requirement. NOTHING ELSE!!!
It is generally recognised (hopefully by you as well) that one SHOULD spend in the region of 10% of the cost of a bike on security. A £1.99 lock is a waste of money on a bike, unless sat next to a more appealing bike with no lock on it. Anyone wanting to take that gamble, then fine.
However, lets remember that there are a lot of bikes stolen every year, and the numbers are not going to go down unless cyclists start thinking more about security, and insurance will never be a reasonable cost until the risk of theft is substantially reduced.
The simple answer is to shoot all thieves. Won't then need to worry about cycle theft, and only need insurance for accidents.
Every bike theft has an impact on the insurance we all pay, whether through a house insurance or with a cycle specific insurer. We all pay for the cost of thefts. If you want cheaper insurance, get the message across that security is important. As such, spending a little more on security is NEVER a waste of money.