Just a ‘from experience’ comment regarding this pic…
The feed pipe (10mm copper) is fed through a notch in the left-most joist under the floorboard above it. The new white-plastic push-fit pipe assembly is then in the void between the joists, but very close to the right-hand joist (and extra wooden 1/2" batten to its left) It is also possibly touching the debris underneath.
Water, when heating and cooling, likes to ‘move’ pipes and introduces noise (taps, bangs, clanks) at every opportunity. I’d ensure that all visible pipes in that pic are surrounded by pipe insulation, not only for heat-efficiency, but also to stop noise from expanding or contracting pipes against non-moving joists/floorboards/debris. Do the same on the other side too.
You’ll never stop upstream/downstream pipe noise unless treated, but if you do insulate on the new sections you’ve installed, you won’t be introducing any new noises. Well worth the effort.
EDIT: **Disclaimer - the recommendation above is related only to the modification to feed heating-circuit water to/from the new towel rail and how to stop potential ‘noise’ from expanding/contracting pipes due to temperature changes within said pipes. From the image shown, the electrical wiring underneath the floorboard level needs immediate attention to protect it from potential damage from above (nails/screws driven into floorboards and into unprotected 13 amp wiring) and also from water ingress should a water joint fail (13 amp junction box immediately below the new push-fit water assembly)
Be very careful here.