Hi David,
It's been a while. Hope all is well in Southern England.
What I do when shooting digital at night (5D) is use a nikon to canon
adapter and use nikon prime manual focus lenses. It makes life much
easier. Do to the engineering, Canon FD to Canon auto focus does not
work, but you can use Zukio, Contax, or Nikon with an inexpensive
adapter purchased on eBay. Mine was $20, and I'll probably get a bunch
and leave them on the lenses...