Swapping radiator.

[Madrab]

When it comes to heat loss then I would say so, 350w is just about the same as say removing a 600x400mm Type 11 (K1)

 

[Fallout]

Another option would be a 1200pplus. So slightly longer rad. A double would stick out too far with need to space the back off the wall further

 

[Madrab]

Still about 250W below the current rad's output. I would never go lower than what was already there unless a heat loss calc suggests it could do.

 

[Fredstudio]

..

 

[Fallout]

As suggested, I would recommend the distance from the wall is changed anyway, for me it is too tight to the wall as it is, there really should be a gap down the back of the rad for air flow. Coupled with the thicker rad then it would be coming out further, unless that's not an option?

Thanks would you recommend 10mm spacing from the back of the radiator to the paneling? I can achieve this by spacing the clips off the way abit when fitting the new rad.

 

[Madrab]

10mm spacing from the back of the radiator

At least - the more space then the better for heat transfer into the air travelling up rather than being absorbed by the wall.