This was about a decade ago now so probably not worth it now tbh

(although I could still do with the £60 back)
I'm still of the opinion that speed is never a factor, simply the misapplication of speed and poor driving. Speed is sometimes an indicator of poor/aggressive driving, but it is an effect, not necessarily a cause. Once upon a time speed limits were set based on the 85th percentile - that is, the limit was what 85% of people drove at or under when left to their own devices, as that was what the road allowed. Sadly that has been discarded recently for whatever reason; conspiratorially, in order to give an appearance of "doing something" and improve the profitability of speed cameras, but I couldn't say. As a result there's now entire journeys where the speed limits are unnecessarily restricting - Skegness to Boston, for example, has no destricted zones anymore, in a 23 mile journey. Ten years ago it had a number of 40s going through villages and the rest was at the national speed limit, with the journey taking maybe 40 minutes. Now it's over an hour because of an artificial limit. As far as I'm aware, it's not made much difference either - the problem is a poor quality road and bad driver judgement wrt blind corners (somewhat of a Lincolnshire affliction, I fear).
Driver education is the only way to properly lower the risks on the roads. Deterrents clearly don't work - how many people do you see talking on mobiles still? - and technical solutions can never properly mitigate human stupidity. A proper driving test, though, that taught driving skills not test-passing skills, followed up with an advanced course and regular re-testing, would do much more than speed cameras ever have.
The government'd even be making money out of it still, and providing employment with the required expansion at test centres. It'd cause too much uproar though. Much easier to sticky plaster the problem with big yellow boxes.