Good to know I can still talk sense occaisionally!
As far as I know, the capacitor is there purely because of space. Cathode bypass capacitors on other sets can be located pretty much anywhere in my limited experience.
Most manfuacturers seem to put things wherever they will a) fit, and b) not cause hum (due to mains wiring next to audio etc.) If your lucky, ease of access will be a distant c) though to be fair Bush were quite good at this.
One of the sets I'm currently working on has all the electrolytics chucked in the chassis corner and clamped together with long leadout wires. Note very repair-friendly...