does anyone know of any after market silencers which might 'improve' the sound of my exhausts a little ? not used to such a quiet bike!
Try
http://staintune.com.au/In my less than humble opinion, the Gold standard in BMW aftermarket exhaust systems.
And yes the stock mufflers on BMW airheads (to the extent I remember as it was all so long ago) sound very much like a fart in a bottle. Staintunes are not loud as such, but much more pleasant than stock.
Oh, and if the price seems a bit breathtaking, I assure you that they are a lifetime purchase. My R100RS has the Staintunes fitted in 1984 (the stock mufflers having excelled themselves in lasting from when I bought it in 1978). Wife's R65/80 got Staintunes around the same time.
My R65 rebuild kit has Staintunes purchased for it in 1989, either its then owner really wanted to spend money on it, or in its case the stock mufflers only lasted 4 years.
The critical thing is that all three Staintune systems are (at least from a functional perspective) as good as the day they were made.