Big thanks to everyone, your suggestions were really useful.
I can echo much of what has already been said. The Topography of Terror is worth a stop, as is the Reichstag. If the weather wasn’t misty/drizzly then the TV tower would’ve been done too.
You can get a “Berlin WelcomeCard” in the airport (SXF) arrival hall which includes all public transport and entry discounts. Nearly 30Euro for the three days. Probably saved a few quid, but it also saved the hassle of buying multiple tickets, having to queue etc.
Berghain was bloody incredible – yes, yes I got in 8) – which I can’t even begin to describe! DVS1 played a storming set.
What happens in Berghain, stays in Berghain.. 😛
Next time will include the Stasi HQ, maybe a trip to Sachsenhausen, and the Trabi tour looked like good fun. Oh and Berghain again too!
Berlin really is a brilliant place – cheap flights/hotels, good food at good prices, easy transport. So much more still to see & do, will certainly be back!