They are about £40 each if sourced yourself.
A very easy job too, right under the plastic cowling - plug and play almost.
Someone is having a giggle with those charges.
Yes they can play up, its fairly common on all cars with coilpacks (almost all petrol cars these days).
The faults I have seen on Hondas have manifested themselves as low RPM stuttering that is often fine at WOT.
Not always the case, but the result is similar - misfire and fuelling error codes/limps that come and go, and can exitst a long time before total failure.
In your case, they have gotten a bit hotter than usual.
No rhyme or reason, they all seem to be hermetically sealed (potted) in resin and quite bullet proof.
On a side note its always worth checking battery negaive to chassis and engine supplememtary earth cabling conections on older cars or those out in the salt all year.