Fuck all wrong with the oldies, a stat, a thermocouple and a gas valve, not much to go wrong and they never usually failed (apart from a thermocouple every few years)
Still got quite a few on my books, although I changed a gas valve on a floor standing Mexico earlier this week £170 odd plus vat, bit salty that for a Honeywell valve I thought
EDIT
I'm talking about cast iron boilers in general, not any specific model
Before you start pissing higher than me again 😍