Brand new M41 d-type gearbox for sale @ £2,217.60

[Derek UK]

I agree that reconditioning costs of a GB + D OD is likely similar in both the USA and UK. Probably the same for J type boxes too. The cost of transporting either from one side of the Atlantic and beyond, plus the return trip, doesn't make that repair option viable, why would anyone consider it? I'm sure the shops in the USA do an excellent job. Parts are available but some are expensive. Recon of the OD's will average out for a company who does a lot of them, with some, possibly most, needing only minor parts replaced but others might be grenaded! Owners of those will consider repairs to be cheap although I think the bill will be higher if a new casing is needed. I believe that exchange units are available by arrangement, depending on stock, which can save you a lot of time for possibly a small premium.
Worth saying that OD Spares and Overdrive Repairs were formed after Laycock closed down the Overdrive department. Both of the owners of these companies are ex Laycock and although running as separate companies, do cooperate with each other in a friendly fashion, or so I'm told.