Well those of you who were here a year or two ago will know exactly why I don't have any no-claims, it's because I've only been driving again since November for reasons I don't feel the need to revisit.
I'm having the work done without going through the insurance for just that reason - although one of the quotes said they could do it for £250 (ie they'd pay half of my £500 excess), they did also advise me that my insurance would probably go up 20%.
Simple maths - the true cost of that is now £250 plus 20% of £600 (£120) plus the loss of 1 years NCB @ 10% (£60) = £430, then I'd be 1 year behind with the build-up of NCB which is more complicated than I care to work out over 7 years, but it makes the price I'm paying privately (£489) look like the best option by far.
The thing which has surprised me most about the situation though, is that if you're not in my exact situation (ie you do have protected no-claims), I would recommend accepting a higher excess in return for a lower annual premium - because a lot of the repairers I spoke to were happy to pay ALL of the excess in return for getting the job (assumedly they add it to the bill to your insurer), but only in the event of a "non-fault" claim - which sadly I couldn't do not having the details of the perpetrator.