What fuse do I need for my ED8525S-SBD microwave?

My DeLonghi microwave suddenly stopped working totally. I opened it up and found a small white fuse at the main incoming power point. The markings on the fuse appear to say T8A 250V. I took this to my local electrical shop and they weren't sure what to give me as replacement. They gave me a 500Mah fuse of the same physical size. I fitted this and the digital display came on which suggests that the old fuse had gone. However, as soon as I tried to start the microwave oven everything went off again - presumably blowing the new fuse. Question is - what fuse do I need to ask for at the shop and is it likely that this is the source of my problem?