Thanks all for your comments and recommendations. Now I'll be the first to admit that I am not nearly as talented, experienced or frankly speaking as good as most on here and it was as such an experiment in some really horrible lighting. I did use the full gamut of the K20s ISO range and the 2 lenses I used (Super Tak 85 f1.9 and K55 f1.8) were never above f2.4
So some examples with some colour tuning:
K 55 @ f2 ISO 3200 (noise visable but nothing as bad as I expected)
ST 85 @ f2.4 ISO 1600 (clearly less noise compared to above but I wonder if the 85 is helping the sensor resolve more!)
ST 85 @ f2.4 ISO 1000 (you have to look for the noise to be honest)
K 55 @ f2 ISO 800 (I was really wary of moving up the ISO ladder at first, this really should have been at 1600 or 2000)
Just to confuse matters I used 2 lenses and both had UV filters on to protect from splashing drink! (it was one of those nights). I don't know if lens quality has come into it, I would consider the Super Tak as a lens needing to be stopped down exposure wise more often than the K but I was at +0.3 EV in all my shots. All said and done, I was happily surprised at what I got at ISO 3200, and in hindsight I should have been between 1600 and 2000 all night especially with the band. Lessons learned? Go high ISO wise, and learn to focus in the dark. Dunno how well the AF would have coped.
Oh and I met a fellow Pentax shooter at the start of the night out and about doing some street shots. Small world! :-)