Most of the 5-valve sets sold here followed a pretty predictable line-up of valves/tubes:
1. Triode/heptode frequency-changer (also called a converter)
2. High-gain pentode I.F. amplifier
3. Double-diode triode detector/AGC/first audio
4. Beam-tetrode or pentode audio power
5. Rectifier
Most of the later generation sets used B9A-based valves, generally the E-series (parallel connected 6.3V heaters) or U-series (intended for series connection in AC/DC sets).
As Sven said, in the typical 5-valve lineup using these valves it is quite possible to identify the correct locations by just examining the internal construction, and I've done that myself in a similar situations.
I'm not sure I could even start to try to describe how to go about it though.
