So there appear to be 3 or 4 options for tools:
1) Bob Paynes RTR Wagon Drill tool from Alan Gibson which is sold out...but may perhaps still be obtained.
2) Micro-Mark Truck Tuner (aka Ed's Tool) from Wizard Models.for £16;50 (plus postage?) and recommended by above by JZ and steve1 Fixed length, cuts at one end.
3) DCC Concepts DCF-BR2 Bearing Reamer Pack https://www.dccconcepts.com/product/bearing-reamers-set-of-two/, well reviewed in a popular magazine, Fixed, cuts at both ends.. £10 to £12 plus postage
4) Tool made by TTTE of this parish http://www.rmweb.co.uk/community/index.php?/topic/111164-knowle-wagon-works/&do=findComment&comment=2306724 that "allows easy and accurate fitment of any 2mm brass bearing in RTR stock. Due to its design it is suitable for OO, EM and P4 gauges." Adjustable, cuts from one end.. £12 plus £1;50 postage. [edtited 22.5.17 to add "TTTE is a.k.a. Knowle Wagon Works, see post 25 below"]
Does anyone have experience of using more than one of these? I am conscious that some (all) of these tools are designed to insert or adjust a brass bearing, whereas what we want to do is insert metal pin point axles directly into plastic.