Gutted!! 1D MK3 Err 99 again!!!

Just got my lovely MK3 back from Canon Uk for an intermittent Err 99 problem, and I used it every day for 6 days, no problem.
The morning of a job, Err 99, ??! ??!!!@@@!!!! !

I tried 2 different lenses, 3 different cards, Err 99.

I am waiting for the office in London to open this morning as this time I want a new replacement body, not another attempted fix.

Is this a reasonable request? I am a pro and cannot afford to have my primary camera have an intermittent fault. They have had one go at fixing it, and failed, they changed a mirror box item and cleaned some magnet, and it still did it.

Luckily I have the 5D to fall back on, but I so love my MK3, I feel like someone has poked me in the eye and ripped my arm off.

Sorry about the ranting, but I feel a whole lot better now.

Regards to all

Rob