I like the mistreted and rusty (has a real feel) and have re wheeled some (though kept the originals in case I sell on) as the wheels do not like running through O gauge points.
Hornby seems to have two sizes (scales?) but either would do.
Photos enclosed (and I hope you can see the ruler)
Crackingjob
Note Coopercraft trucks for comparrison (yes I know they are blue..but thats why they were cheap 2nd hand!)
Rewheel method 1. Binnie wheels and plastic tube glued toether over the original axle..ideal as larger stock is a little heavier.
Method 2. Brandbright steel wheels...ideal for smaller stock that need weight
Earning revenue!