I think I stuffed up
 

Did a clean on the throttle body & after removing all the carbon with carby cleaner there were some small ridges that I polished off with autosul & the throttle body was quite shiny compared to before.

Now she has inconsistent idle & poor throttle response under 2K.

Will have another look at it tomorrow. Should I unpolish?

sounds more like there is a vacuum leak somewhere. Double check very carefully how everything was put back together. Also, look to see if you knocked off any wire harness connectors while you were either pulling off the TB or putting it back on.

If its not egas, also check the idle control valve, some crud may have flowed in there.

I come from a background of Japanese cars, but.....

Throttle bodies may have a "plastic" layer installed right where the throttle plate rests when closed. This serves as a "gasket" to ensure complete closing, with idle air supplied from a bypass. It's a common error reported in certain forums to over-clean throttle bodies with harsh chemicals (e.g. carb cleaner) which removes this carefully-manufactured plastic layer. Then the throttle body will forever leak a random amount when the throttle plate is closed. In the US there's a special "throttle body" cleaner sold that's less harsh than carb cleaner, ostensibly to not remove this plastic liner.

Sorted itself out. After daily driving for a couple of weeks it eventually returned to normal.

Got me stuffed.

if you are concerned with fuel system cleanliness, may I suggest marvel mystery oil. this stuff is great at cleaning out carbon and varnish from fuel systems. I recently purchased my boxy with under 50k on the odometer. as I was driving home from the purchase, I tripped a CEL and read it with my el-cheapo code reader. o2 sensor.... so being the diligent owner I am I ordered 4 o2 sensors. while waiting for the order to come in, I added 4oz of MMO to the gas with my refill. the idle smoothed out CEL went out and the performance increased (no dyno test, so don't ask). sometimes some of those old school remedies still work out, now I add a few ounces to the gas as a preventative measure. now I have 4 brand new 02 sensors sitting in their original packages at the house (will keep them around for when they are really needed).