Thanks Andy the best price so far is from linearmotionbearings2008 at
192 pounds which sounds ok. They say the bearings are Japanese angular contact Z4 grade.
All these spindles look the same to me!
There are plenty of inverters on ebay for not too much money and good makes like Mitsubishi, omron and moeller.
Are the ER20 collets detachable and maybe fit better quality ones in the future?