Problem solved! Many thanks to someone on the Model Engineer site for suggesting that I try Goodwin Technology for the repair of my Mitutoyo DRO system.

I got in touch with Darren Goodwin who suggested that I sent the DRO and scales to him for examination and possible repair. He said that the maximum charge for any repair was £125 plus VAT and £15 plus VAT for carriage back to me.

My DRO was returned after being repaired for a total price, inc carriage and VAT of £72.00, which beats the £400 or so that a new system would have cost.

I've not used Goodwin before but they will certainly be top of the list in future.

Brian