I haven’t seen one of these Oxford wagons, and I’m highly unlikely to. However there are a number of pictures on RMWeb which show one being disassembled.
The wheelsets look to be standard plastic spoked wheels on steel axles. Therefore you should be able to simply pull the existing wheels out along the axles, and set them accurately using your favourite back-to-back gauge. If you feel that they may be a little loose after adjusting them, then a spot of superglue or Loctite at the interface between the wheel and axle will fix them securely in place. It’s a procedure I use to ensure all of my P4 wheels stay where they are intended.
To my eyes, the Oxford tyres look excessively thick as well. As a next step you may want to consider sliding the Oxford wheels off the axle, and replacing them with ones from (say) Alan Gibson. The Oxford axle should be a standard 2mm one, so the new wheels should just slip back on. Then you have decent finescale wheels on the over-long axles which concerned you.
Paul Willis (10060)