The excess is just an amount which determines whether you pay or the insurance company pay. Beyond that (ie greater than the excess then the insurance company will pay - provided the repairs do not cost more than the vehicle is worth). Less than the excess - that is what the insurance company expect you to pay yourself for any necessary repairs. It means that the insurance company don't get bothered with claims under a certain value.
Don't forget - the *no claims bonus* is just that... it's not a *no blaim bonus*... Even if you are not at fault, if you claim then this might affect your no-claims bonus (unless it is protected... but that's likely to be only for one or two claims anyway).
PS My car was recently damaged by a driver who didn't even bother to stop and leave his/her details.... The assessor determined that the repairs required would cost more than the value of the car (well, they do go for replacement wings, doors etc, instead of pulling out dents etc) so it would be uneconomical to repair. I would have ended up with no vehicle, financial reparation as per their estimate of my car's worth and a lot of hassle.. I ended up deciding to pay (in a local garage, rather than a big dealership) for the necessary repairs, which was going to be less than my excess, just to keep my lovely car.
The big accident assessors usually just recommend replacement parts, rather than repairs and the rates appear to be seriously inflated .....