I would strongly advise against use of a 120 volt string of lights from 230/240 volts by means of a rectifier diode.
Whilst one might expect that this would give a 120 volt equivalent supply, this is not the case in practice.
Any 120 volt lamp, or series string of lamps, will be significantly overun if connected to 240 volts via a diode.
Anyone who doubts this should try a very simple experiment.
Obtain 3 similar 240 volt GLS lamps.
Connect two in series to the mains, and connect the third lamp to the mains via the diode.
The lamp on the diode will not light at full brightness but it WILL be significantly brighter than the ones in series.
The use of 240 volt lamps, or series strings totalling 240 volts, from a diode is fine.
The effective voltage is appreciably less than 240 volts and the lamp life thereby extended.
To use 120 volt strings in the UK the best way is via a 110 volt building site transformer.
This will slightly extend the lamp life as the output is 110 volts rather than USA 120 volt mains.
The fact that these transformers have an earthed center tap gives a useful extra factor of safety, the worst electric shock that you can get to earth is 55 volts, which is not normally dangerous. Still take though, just in case !
