This is quite common in many homes.  If you want to address it you can or just leave it and let the RCD do its job.   Modern cables will last for decades touching domestic dwelling heating pipes as it probably only get to about 55 degrees  Celsius
However if you want to address it then get some of the following
15mm pipe insulation
22mm pipe insulation
1 * All Round Band

Now this is where the challenge starts.  Get yourself a hammer and a set of pry bars and a sharpie.  Start to lift floor board, de-nail and mark up for joist positio,n cables and pipes.  Then insulate your pipe work and cable clip/allRound band the cable.  Re-fix floor boards CAREFULLY using screws,  You may need to drill, pilot hole and counter sink.  Floor dependant.   Rinse and Repeat.  It is an easy job but very time consuming and you may also discover other nasties under the floor boards like copious amounts of rubbish and rubble.   CAVEAT Asbestos awarness

This is quite common in many homes.  If you want to address it you can or just leave it and let the RCD do its job.   Modern cables will last for decades touching domestic dwelling heating pipes as it probably only get to about 55 degrees  Celsius
However if you want to address it then get some of the following
15mm pipe insulation
22mm pipe insulation
1 * All Round Band

Now this is where the challenge starts.  Get yourself a hammer and a set of pry bars and a sharpie.  Start to lift floor board, de-nail and mark up for joist positio,n cables and pipes.  Then insulate your pipe work and cable clip/allRound band the cable.  Re-fix floor boards CAREFULLY using screws,  You may need to drill, pilot hole and counter sink.  Floor dependant.   Rinse and Repeat.  It is an easy job but very time consuming and you may also discover other nasties under the floor boards like copious amounts of rubbish and rubble.   CAVEAT Asbestos awarness

Sergio Fernandez said:

Re-fix floor boards CAREFULLY using screws

Not a bad idea! It depends a bit on the finish required and whether it is carpeted or not.

In the instant case, the boards may have been lifted previously, but cutting across an existing board and even worse, coping with tongue and groove is a nightmare. Any tips?

Not all the treasure under the boards is nasty. I have ancient porcelain fuse holders, an empty Woodbine packet and matchbox. They can help with the history of the building.

P.S. make sure that the cat(s) are out when you put the boards back. :-)

coping with tongue and groove is a nightmare. Any tips?

I have two techniques . For modern (softer thinner) solid softwood boards, a Stanley knife (other brands are available) with a nice fresh blade will usually slice through the tongues with a few firm strokes. Failing that a oscillating electric saw (e.g. Fein although mine is a different brand). In the old days you could get a 'floorboard saw' that had teeth around a curve on the top of the blade, which you could use to start a cut from one side, to cut through the tongues, but that could he hard work if the gap was thinner than the saw blade.

  - Andy.

p.s. never try your favourite tenon saw, tiny bits of grit inevitably accumulate in the gap and will ruin the teeth surprisingly quickly.