After investigating your enquiry with SEAT UK's Technical Department, they have advised that they have had isolated incidences/reports of this nature in the past, however, upon investigation it has been determined that the cause of the concern is not related to the vehicle wiring or fuse/fuse box . The main reason for the fuse/fuse box to heat up is because the cooling fan is constantly running due to the fact that the engine is overheating which is often not picked up by the customer. Therefore, further investigation into the cause of overheating is required. Once the root cause of the engine overheating is rectified the cooling fans will no longer run constantly therefore, the fuse and fuse box will no longer heat up.
I hope this information is of
help to you, however, if I can be of any further assistance, please do not hesitate to contact me