I've moved it to the back of the front seat and its better.

The guy who makes it also has a relay that switches the thing off when you apply the brakes.... that would mean you only get the buzz as you initially enter and then complete the turn - not when waiting at lights or while slowing. I'll be doing that for sure.
Between the two mods (and possibly moving to the back seat as has been suggested) it should be OK. I have to be something because I'm always leaving the blinkers on.

The variable control thing is OK, but I've realised that it would be necessary to apply diodes to the circuit to keep voltage the same for the indicators themselves (otherwise presumably they'd go dim - its a direct circuit - no relay).
I'm no expert so I think I'll just try the first two ideas..
It needs some taming this thing - otherwise its like sitting on a jack hammer. Ow.