I have decided to replace the wheel sets with bachmann -- at
1 gbp per 10 axles it is not really a burden.As the overwidth occured where a curve departed from the removalable 4ft bridge I was loathe to lift it (araladited down to make the cut) but damn it ! so I lifted it. To my surprise the length of track involved was not marked Peco but MQ. I have no idea what this is but the chairs are slightly diferrent from peco but the design is otherwise identical. Having replaced it with Peco Ni things improved but the tripping still occured on a much less frequent basis.
If the UK postal strike doesn't screw me up I shall be able to confirm if bachmann prevails. Certainly B'mann locos are better lookers and smooth even if their traction is poor and I have been obliged to sell on two Hornby locos (A3 and Un R/B Patriot) because their cabs stood so high -- just like the wee GW 29XX PT funnel.
Must also say that I am delighted with the Fairburn 2-6-4T -- like the Ivatt Cl 2T it pulls it's weight.