It's an interesting point. The law actually allows a competent person to work on their own gas systems themselves but doesn't define exactly what that means. I've seen people claim that it only narrowly applies to previously qualified Gas Safe engineers who have allowed their registration to lapse but I think that is a stretch.

Also, I think the idea would be to install an air source heat pump rather than resistive electrical heating.

You could use a heat pump if your radiators allow it.