Thanks to one and all for the (very rapid! replies.
Les - Thanks for this. I'm currently using a "Paterson High-Speed Print Washer" http://www.patersonphoto.co.uk/accessories...ge2.html#bottom which I acquired 2nd hand along with the rest of my darkroom. I think it works in a very similar way to your suggestion and I have no complaints except the limited number I can do at once. Rigging up a few of your version and having them going in parallel might be a way to go.
I take your point about washing out the brightener. I have been washing with a fairly aggressive water flow up to now. Now might be a good time to tone it down a bit! :-) What would you suggest for a suitable washing time (water temp is usual UK mains supply (i.e. Brrrrrr!).
dnmilikan - Was this a vertical slot washer? If so, did you have any issues with FB paper buckling?
Aggie - Are these made by Paterson like the link I have above, or someone else?
I notice that nobody who's so far replied uses a cascade system. Should I take that as indicative of something?! :-) I managed to find a shot of a professional cascade online at http://www.richards.uk.com/pwash.htm (top left). Any thoughts on my DIY flavour?
Again, thanks very much indeed for the information!