Ok, so the VM cable now ran up the exterior of the house to the loft. Being designed for (among other things) RF signals from antennas, the cable *should* cope with being mounted outside. I’m shortly, however, going to run a whole bunch of CAT6a networking cables via the same route which may not be so tolerant. The cables needed a cover to protect them (also, externally mounted exposed cables look horribly untidy).
There are products available specifically for this job, but they look a bit too “industrial” and I found them inexplicably difficult to source. The answer?: pipe covers. We had a new gas boiler installed when we moved in which had to be installed in such a way that we ended up with a couple of ugly copper pipes running up the exterior of the house. It turned out that there were covers available for the particular sort of pipe-clips the gas engineer used, and it didn’t take me long to realise that I could use the same types of clips and covers for the cabling.