How'd you go getting the TWS Dave?
I recently faced the same issue of either paying $38 a litre from BMW, ordering it from the US and paying ridiculous shipping or switching to Liqui Moli. I did the latter and to be honest I can't flaw it, no difference whatsoever. Was perfect at the track too.
However, I do feel somewhat dirty using non authentic oil (despite some track dedicated E46 M3's running Liqui Moli).
I'm keen to switch back to TWS if I can get it locally for a good price... $70 for 5L is awesome!