There should be no problem using a standard IEC lead with them. The rear panel layout on page 5 of the data sheet shows the connector, and it looks from that as though it is a 3 pin connector, although I have seen connectors like that with no earth pin. If there isn't an earth pin, there is no harm in using a mains lead with an earth connector.
The fuse marked T1AL250V is a slow-blow 1A fuse, for use in circuits up to 250 V. If that is blowing, it sounds like something is wrong.
However, the power supplies for any active speaker will tend to have quite large turn-on surges. The surge may be a lot larger in the UK than the US where those monitors are designed, because of the larger voltage and the lower impedance of the wiring
I suggest that you replace the fuse, and, before connecting it to the mains, measure the resistance between the live and neutral pins, both on 120 V and 240 V settings. Post what you find here and we will try to help.
The fuse in the mains lead plug is only there to protect the mains lead, so you can use any fuse up to 10 A, as 10 A is the rating of those IEC connectors. There wouldn't be a plug fuse fitted if it were sold in America.