If a fuse blows (even more so if it's repeated), the amp is telling you something is wrong. The most likely suspect is a bad power tube or too hot a bias setting. Although this should blow one of the tube fuses first, there are a number of reasons why it might blow the mains fuse instead (the wrong rating of fuse in the power tube fuse holder for example).
I suggest replacing all the power tubes, biasing your amp correctly and report back.
Hope that helps,
Rob