I haven't done much with long cables, perhaps someone else could chip in.
BTW, would it be direct from source to display device? Adding and wall plates etc. would be a risk.
Yeah it's going direct from source to display. It will be buried in a dry lined wall and across a ceiling. I'll probably get two tbh and test them before final install.
Work on maximum of £2 per meter. All they need to be is High Speed Hdmi. If being fitted in wall use the saving to run a couple of cat 6 cables at same time as both a backup and future proofing
I will take care with the replastering etc. I'm going to remeasure to see if I can get away with maybe 7mtrs. Wether that will make a difference or not I'm not sure.