see - http://www.thatcham.org/security/index.jsp?page=75 for security device info and ratings.
Garage security doesn't make any difference, I think the underwriters look at garage as the lowest risk, but lets face it if they want to get in they will. Plus Bike underwriters aren't geared up for assesing the effectivness of building security.
Clothing, I see your point with that one, it does make sense but would be hard for the underwiter to be 100% certain you were going to wear the gear on every journey, where as security (alarms etc) its always on your bike and most will arm automatically, on medern bikes, anyway. On my companies list of products the only locks to get are oxford, abus, mottrax. alarms, datatool, meta, spyball. The xena disclock alarm will get a discount with some underwriters. the thing to remember, what works for one underwriter may not work for another, what works for one underwriter with one broker, may not with the same underwriter with a different broker.
Daytime riding, the problem with that is that it only takes one journey stuck in traffic, and your in early evening, and there you go you have just invalidated your policy.
Do the IAM, that helps, also joining an owners club can help too.
Don't quote 500 miles a year, try something nearer 5000, companies will look at a rider who is on the road for 500 miles a year as a higher risk to the u/w than somebody who does 5000!!
NCD protection can bring the prem down!!
Also a vouluntary excess may be saving you no money whatsoever, so check on zero vol.
Hope this helps!!!
Ciao for now!!!!!