Clubsport Fuse size?

[gsinky]

After inspection of my car this evening after a weekends sprinting I have noticed the fuse casing(for the ignition system?) has melted. The fuse itself didn't blow but the plastic round it melted. I suspect this was caused by it touching the header tank, but any other possible suggestions are welcome. It is located behind the ignition kill switch on the left handside of the engine bay, just behind the cockpit bulkhead. I think the melted one is 30A (green) but I am slightly suspicious that this is a too large a rating for the task it is doing?

Any suggestions?