There is slim pickings out there in the very big sizes i'm afraid. Your best bet would be an On One 21" Inbred for around £150 for the frame. The odd one turns up on here in that size.
I'm 6'7" and have a 21" Inbred, 22" Salsa & 23" Rockhopper all in 29er but i don't think any of them have rack mounts etc and the last two will never turn up for sale as they are very rare (in the largest size).
I do have a Trek hybrid in massive size (63cm - same as my road bike) which i never use (it's sat in my office) but it's rigid and hub geared (rear coaster brake so not even vbrake mounts on it) so not sure how appropriate it would be for your needs - does have rack mounts though and Nexus 7sp hub. Trek Navigator S300 - around 2004/5 model. Barely used as it was an insurance replacement.
I'm just south of Brum in case you have any interest - and any other tall chap is always welcome to come over and test out the big 29ers for size as i know how hard it is to get test rides on the biggest bikes.