Quick electronics question

[cropwell]

otherwise the base is left floating which should never be allowed to happen

I should have remembered the lessons I learnt in the '70's when I was doing circuits with 4066's and leaving inputs floating, with unfathomable results (until the penny dropped). My emulation software is crap and out of date (IC library is woefully lacking), but it is OK for quick checks.
Yes, I put the voltmeter on to show what was happening across Q1 and did wonder why, but with the SW there should not be enough Ib to turn Q1 on. (???)

Even with strapping the base of Q1 to Gnd there is an e-v voltage of 10v with the switch open - curious... Putting a diode in series with the LED puts the emulation right, so I am going to presume that the circuit emulator has a large reverse leakage on the LED.

[Kitwn]

Even with strapping the base of Q1 to Gnd there is an e-v voltage of 10v with the switch open - curious... Putting a diode in series with the LED puts the emulation right, so I am going to presume that the circuit emulator has a large reverse leakage on the LED.

That agrees with LEDs having such a low specs for reverse voltage, usually only 5v.

So we can finally give m_c a definitive answer that might actually work! Strap the transistor base to ground via a large-ish resistor to avoid letting it float with the contacts open and add an ordinary diode in series with the LED.