Boiler outer casing getting very hot - Ideal Classic RS40?

Hello, I have a Ideal Classic RS40 Boiler and the outer casing seems to get very hot.

It seems to be working fine so I am sure this is normal but if anyone reading this has the same boiler I would appreciate their view.

I have just had the thermocouple ? changed although I am sure it was getting as hot before hand.

Thanks in advance