I think you have 2 options:
1) Your Nord should have a switch in the transformer that converts it to 230v, but if you do that, you also need to change the fuse for a different value. See:
https://www.norduserforum.com/post140032.html#p140032
(Fuses are all Slow-Blow type). And make sure that you switch it back on your return!
2) Get a voltage converter that converts 230V to 115V and forget about changing fuses and opening the board to switch (sorry I can't tell if the one you posted is any good). Make sure that the power rate of the converter is above the power required by your instrument (specified in Watts on the plate at the back of the instrument).
Whatever you do you will also need a "US to UK plug adaptor". That only converts the plug shape, not the voltage!
If you go for option 2 you could also bring some fuses in case your transformer breaks and you decide to change the internal switch to 230V.