I tried similar, I think it was a 'mini bomb' or something like that from Nippy Normans. Had to buy the expensive adapter lead too.
Anyway, didn't work. Worked okay just with the ignition on, but once running it would only sound once then cut out completely until the ignition was recycled. Returned it and tried a replacement with exactly the same results, so put the original back on which works perfectly.
Appears to be a canbus issue, but NN's claim to have sold hundreds without any problems, so chances are you'll be okay, but it's not 100% given.