A little tip for fixer. When you snip the end off your 35mm film to load it onto the reel, keep the clipped end. Mix up some new fixer according to the strength you intend to use. (1:4 for ilford). Put one spot of fixer on the clip and it will make a clear spot. Now dip the whole clip in the fixer and time it to see how long it takes to clear completely so you can no longer see the initial spot. probably be somewhere around a minute. This means that with brand new fixer 2 minutes is ample clearing time. However as the fixer ages, clearing time gets longer. Use your film clips to keep track of your fixer and when the initial time to clear hits double the original fresh fixer time, junk it and start again. Aged fixer time to clear can be 2 minutes, so appropriate time in fixer is 4-5 minutes to be safe at normal temperatures.
How big? I work very comfortably in a space 1.3m x 2m.My proposed darkroom is perhaps too tiny
An even quicker and dirtier way is to use the "positron" ap for iphone which inverts what the camera sees.A quick and dirty way to preview your images is to shoot them against a bright white background with a digital camera or smartphone