Doug,
There were as many different shed layouts as there were sheds. The designers were for ever trying to produce their ideal arrangement, but they were always short of money and had to compromise and make do with what they had. As a result most engine shed layouts were unsatisfactory, probably too small, derelict to some degree, ill equipped and lacked decent accommodation for locos and staff alike.
If you provide covered accommodation for about half the locos allocated, suitable facilities for watering, coaling, turning, and ashing out, you have all the elements.
Boiler wash outs, as in the BTC film "Wash and Brush-up" mentioned earlier only took place about once every two weeks and at main sheds, probably not sub sheds. However it is an excellent film and I strongly recommend anybody to get hold of a copy of it on Video or DVD. It really explains the workings of a loco very well. I suggest that if a few more of our preservation societies had insisted that their (non BR trained) fitting staff watched it and applied all the principles explained, there would have been far fewer problems with leaking fireboxes and foundation rings a few years ago, and a great deal of money would have been saved.
Recently, I have found that a number of useful books on engine sheds have been offered at very reasonable prices in local bookshops.
In particular, may I recommend any of the series of three books on GNR Engine Sheds by Griffiths and Hooper, published by Booklaw. Do not be misled by the title, the development of all the GNR sheds right through to the end of steam is covered in graphic detail, so LNER and BR practices are also covered. I have managed to find all three volumes in recent months, all on offer at virtually give away prices.
On the second hand market, look out for British Railways Engine Sheds - London Midland Matters by Hawkins, Hooper and Reeve. The Irwell Press publishes a series of these books and I also found a slim booklet "British Railways Engine Sheds-an LNER Inheritance , by the same authors.
You could try Amazon or Abe Books for these. Preservation societies often sell second hand books at reasonable prices and these sort tend to stick on their shelves, so try haggling.
All the above books have black and white photos of all aspects of sheds. The last one is particularly good on cenotaph style coaling plants. All of them have details of turntables fitted, types of coaling plants, ash plant, track plans and the like.
If you want colour photos of BR shed scenes, one to look out for is Steam on Shed by John Stretton, published by Chancellor Press. This has lots of good photos taken in the 50s and 60s, but lacks detail on shed facilities.
The biggest problem for me was finding enough space on my layout and working out how to fit in everything that I decided that I needed.
Colombo