Thanks for the info - not going the dog box route, just too damn expensive. Cheaper to keep two boxes and service one each year. The change is really good anyway, and the whining dogs would be hard to live with.
Some more info:
Gemini do a gear kit, not a box - you need to rebuild the box (expensive, may as well buy a new standard box)
The Hewland stuff is a gear kit, and is the innards of the Ralliart Dog Box.
Quaife DO have a gear kit too, and so do Monster as well, but both are too short on the gearing (as is the Hewland and Gemini stuff, dunno about Quaife) - well it is too short for European circuits anyway.
The RS2 box sounds ideal - just have to accept annual rebuilds

Although both Ralliart and PE think that I may have had one of the bad batch of boxes with the pre-load issue, as it has been gathering swarf from day one on the mag plug.
Ralliart also told me that the reason these boxes fail is temperature, so we will be fitting an oil cooler and electric oil pump for the gearbox too.